I think the way Magisch answered is okay for a lot of SE sites, but we need to be more strict. This site is sorta getting out of hand as far as answer quality is concerned... I think that we have discussed some other cases here, in which deleting is also necessary. As Jefromi commented:
we take that approach mainly because it's an easy rule to apply, and the costs/downsides are minimal (we don't have an overabundance of horribly bad partial answers). The balance is very different here, so I would not expect the same decision to be best.
The bold part is my emphasis on it. The balance is very different here. We get a lot of answers that fall into one of the categories below, and should be removed instead of just downvoted/commented. Because we get a lot of passerby's with Many Opinions that don't know these answers are bad for our site, and upvote them anyway!
There is enough written on this already. There's also this answer and I recently wrote this. Recently, we had another one of those questions where people were writing non-answers: How can I get my sister to stop asking me to help her smoke?. If the premise is 'I want to ask her to respect my wishes and stop asking me to help her smoke', the 'simple' answer isn't 'go get her cigarettes anyway'.
If an answer goes against the premise of the question, it should be flagged as NAA and be deleted.
Answers that aren't offering an Interpersonal solution should be removed
Make sure to take the time to click the link in that answer. It has been policy since August! to remove answers that aren't offering an Interpersonal skill.
This site is interpersonal.stackexchange.com, not ihaveaproblemandwantanysolution.stackexchange.com. There's a definitive difference.
This ties closely together with 'not honoring the premise of a question'since posting here holds a premise that an OP is looking for an Interpersonal solution.
If an answer is not offering an IPS solution, it should be flagged as NAA and be deleted.
This goes hand in hand with the discussion about a back-it-up rule. The basic outcome was that there should at the very least be some
One-line answers aren't likely to be backed up with experience, sources or solid reasoning. But, if they 'are' an answer to the question, we should use VLQ flags for these answers, not NAA flags to get these answers deleted.
We can upvote answers if we think they are good, there's no need to confirm that by writing another answer that basically states the same.
I don't think we can flag answers as a duplicate though, so this will probably require a custom mod flag. Make sure to provide a 'link' to the post it is a duplicate of.