In general, I think tags should only be used when they are relevant to the specific situation in the question (and that relevance is clear in the question). Like tag help says:
A tag is a word or phrase that describes the topic of the question.
For example, I could ask a question about "how to come out to my religious parents about being agnostic?". That situation definitely has parallels to situations that many LGBT+ folks have experience with, and I'm sure some of them would be able to give great advice based on those experiences. However, my question isn't about anyone being LGBT+, so it wouldn't be appropriate for me to add that tag. (On the other hand, if this was a common enough topic, we could decide to create a tag like coming-out that could be used by both types of questions.)
Another example is how autism-spectrum is used. Questions tagged with that are either:
- focused on an interaction with a person on the autism spectrum (whether OP or someone else)
- asked by someone on the spectrum who wants to encourage answerers to take that into account (even though the situation itself might not be directly related to them having autistic traits)
But, it does not mean "I want autistic people to read this question".
For the original version of your post - the explanation you added looks to me more like that last reason ("I want LGBT+ people to read this", rather than "this question involves someone who is LGBT+"). So I can see why someone felt it should be edited out. I feel like it's almost a meta-tag -
The reason meta-tags are a problem is that they do not describe the content of the question. They describe some other aspect of the question, like the author’s skill level, or the author’s motivation for asking it, or generally what “kind” of question it is (poll, how-to, etc.).
because it's not actually describing the content but rather who you want to answer.
Plus, if answerers don't have any info about why it is relevant to your situation, they can't tailor their answers for that, so the tag might as well not be there. The question could still be found by anyone searching IPS for "new name", but just adding the tag won't guarantee that the answers will be applicable to the trans community (as pointed out in a comment there's many other reasons a person might change their name, which would probably involve different sorts of conversations).