TL:DR: A lot of this could have been (should have been?) prevented by:
- Understanding that Interpersonal Skills isn't meant for solely voicing opinions of any sort, so if questions are asking for that (who's right/wrong), they should be closed.
- This means that questions should be written clearly, so that answers can honour the premise (even frame-challenges should to some extent). Opinions should be backed up with experience. Clarify the question so that the situation described leaves no room for disambiguation, stick to the premise of the question and write well backed up answers.
- Answers should be about Interpersonal Skills. Telling people how to feel or whether or not they are responsible isn't that. It's interesting to know why they feel the way they do, but that discussion doesn't have a place on the main site or meta. Chat is your best option.
I fully agree with some of the answers already written here, and disagree to a certain extent with others. But I'd like to point out, that some of this drama could have been prevented. I'm going to take just one example question from your question here, because otherwise this answer will become way too long: How can I avoid the awkwardness of a returning player who wears a low-cut shirt?
First of, your title question: How to talk about “who is responsible, who is to blame”?
If you ever, ever find a question boiling down to that, and only that, just close it. It's primarily opinion based, and not about interpersonal skills so it will be off-topic as well. As for the first example question you linked, that question is lacking details and the two example sentences together with the title basically leave it open to discussion and make it too broad as well.
How can I approach this situation in the least awkward or least offensive manner?
Isn't really asking for help with a particular Interpersonal Skill. At most, it is asking us for a list of possibilities. It doesn't invite good, long answers that explain how and why. It doesn't invite people to back up their opinions with experience or provide sources. It doesn't invite sharing experiences over opinions. Basically, it fails to meet guidelines for good subjective questions as set out in this blog post.
Then, the bit about the situation: My concern it that how can we find a good answer if we don't even agree on the situation?
There are 3 things that can help here, the most important one being that the situation is clear in the question itself. It should leave no room for interpretation, it should need as little interpretation on the answerer's side as possible. Right now, as discussed above, the question could use a whole lot more detail to achieve that. I know people hate it when I go all pedantic on them, or ask for minor details like your most hated gossipy aunt, but I've seen it work. It's a lot easier to achieve the next 2 steps as well, if the question is in good shape, to begin with.
The second thing is to stick to the premise of a question. This does not rule out frame-challenges. It does mean you can't simply tell someone to not do the stupid thing because the stupid thing is stupid, and your awesome thing is better. To quote from the answer I just linked:
I believe that responding to "How do I $x?" with "Doing $x is inexcusable and/or evil." is inappropriate, and should be dealt with using downvotes and/or deletions to prevent shrill bickering over our differences from obscuring useful information that the questioner is seeking.
If you really want to write an answer to a question asking about e.g. how to apologize with 'It wasn't your fault', please just pass by the question. If you' think you can actually write a frame-challenge here, explaining to the asker the negative ramifications of apologizing by sharing experiences and drawing strong parallels between their situation and yours, then you might consider writing a frame-challenge. But if you decide to do so, part 3 becomes very, very important.
Part 3 is about the most unpopular thing here, because it requires nitpicking, maybe even sharing stuff you don't want to share on the internet, or ruling out 'common sense' answers. It is to back up your answer. I know a lot of people here aren't fond of me asking them to back their answers up. But this goes 2 ways: if you have an unpopular opinion, but are able to back this up with a watertight experience (e.g. you asked a girl to wear a higher neckline, in such and such a way, and it went badly wrong, so you'd advise against ever doing that) that is an answer. Bonuspoints if you can draw strong parallels between your situation and that of the OP, like explained in e.g. this meta on how to write experience based answers
It is, however, very, very different from saying:
I think it's easiest to describe this with a real world example: If a woman wears a shirt which shows her cleavage and maybe a short mini-skirt then I think she should not be surprised if men look.
That's not an interpersonal skill now is it? Think about it, what question does this actually answer? Who is to blame for looking? Is that an Interpersonal Skill? Not really. We do allow etiquette questions, so if you're asking about situations in which there is a specific dresscode, then yes, maybe, just maybe, this can be worked into an answer... but for the question discussed here, it isn't.
You can ask people to back up parts of their answers too, to explain the experiences or sources behind their reasoning. You can refrain from upvoting until the desired clarification is present. But remember, there's a difference between asking 'could you explain why you think the way you think' and commenting 'I think differently, I disagree with X, Y and Z'. Catija wrote a good meta answer with a good example on how to phrase a comment.
For your third question: How can we discuss this openly? I don't think deleting comments and answers is a solution for this.
It was already pointed out that comments aren't for discussion. So, yes, comments discussing this stuff are deleted, and that's good. This site isn't the place to discuss. Take a look at some 'rules' a CM set for this site a long time ago in November 2017. They're not enforced or something, but if this site continues to fail meeting them, it will eventually get shut down.
I think it's perfectly natural for people to have opinions. I have a lot of them too. I commend you, Edgar, for wanting to know where other people's opinions come from, like you explained in your comment underneath one of the answers here:
It seems there are many questions like this and I like to understand why people think the way they think. In this case: Why does the guy feel guilty? Is that not a reasonable question?
It sure is a reasonable question to ask yourself, although it might not be a good question to ask in a comment or challenge in an answer. Guilt is something like religion or veganism, it shouldn't be challenged. This goes for all the 'feelings' on IPS. Please don't tell people how to feel, instead, provide useful guidance on how to proceed with those feelings. You stick to the premise that there is guilt. If the question is about 'how to apologize' however, you can point out apologizing might not be the best way to remedy this guilt, that it may lead to more guilt because you're about to do a stupid thing that in your experience won't end well.
It indicates a problem with the question in this case as well: A lack of detail. Indeed, what makes the guy think the way he does? Is there information missing here (maybe a cultural thing? Prudish guy?), or are we dealing with someone that overreacts and overthinks the entire situation? Sadly, it's very difficult to write good comments asking the OP to clarify this part of their question, but it's not impossible. I'd personally go with something like
I see evidence of only one incident, and I don't really get the severity. Could you perhaps clarify why you want to apologize/ask for a higher neckline? Is this related to something cultural? What makes you want to do what you want to do, and why are you afraid it will go wrong?
But remember, even without this information, it is important to stick to the premise of a question. If you really want to understand someone's motivations, your best bet is the chatroom. People can offer you possible explanations (though never the one and true answer, because we're not mindreaders).
Try and stick to the three steps above (clarify the question so that it leaves no room for disambiguity, stick to the premise of the question and write well backed up answers) yourself, and help other people do it as well, and hopefully, the site will improve over time...