If I have a possible solution for someone's question that worked for me when I had a similar issue, but I am not sure if my solution would work for that person.
In that case, should I post it as an answer or a comment?
I have seen people giving answers in comments. What is the reason for that?
Comments should never be used to answer a question, but sometimes they are used to give a hint to the OP or any users who could give a more complete answer. Sometimes, users who think the question should be closed write a short answer as comment.
You could write an answer saying what you did in a similar case. It would be better if you make an answer that match the question, for example showing what you would do in the OP's case.
I've given answers that were I guess too short and were then made into comments, so that might be where you are seeing some answers being comments. But yeah in general I would say that if it's an actual answer, make it an answer.
As the ones you probably seen "giving answers in comments" I feel I should answer, too. There are two situations when I do that:
There is my close vote on a question. I don't provide real answer then, but try to direct people to the right part of the manual / correct site to ask a question / hint them what to test et cetera. And if it solves OPs problem directly? Well, the better for him.
I have no time to write a proper answer, or to test if my solution fits. So I post a hint as a comment, and when I have time I try to go back to it and write a full answer - or upvote the one already given in the meantime. That way my knowledge can be used (or discarded) as fast as possible, without degrading site's quality. And if you see my hint comment on an unanswered question, ping me about it using @ notation! Or use it to write answer yourself and ping me to check it ;)
Second point happens more often than I'd like it, sorry.
