I've noticed that some users, after answering a question, add a comment to the question promoting their answer, and praising the OP on the quality of their question. Is this considered bad form?
Without getting into any specific examples, I think the answer is clearly: it depends.
Giving credit to someone for asking a good question when you really think it is a good question is a great idea. If it is sincere, it a polite and honorable thing to do. For example, I doubt Eric Lippert has much to gain directly by praising people's questions but he sometimes does it. But if a teacher were to say "good question" after every question it would become meaningless.
Similarly, if you tell your superiors "great idea" for every idea they have, people around you are going to notice that you are a sycophant and probably think less of you. On Stack Overflow if you are insincere and say "great question" when its not a great question other users might think either you are not a very good judge of questions or that you are pandering to the author.
As far as directing the asker to your answer, some askers need very specific help in understanding that a particular answer, perhaps your answer, addresses the conceptual problem being discussed in comments. In such a case, it makes a lot of sense to "connect the dots" for the asker.
In other cases, a "see my answer" comment might be little more than "that kid" who always raises his hand in class really high, waving it around, saying "I know! I know!"
So we really cannot say "you said 'good question' or 'see my answer' and that is bad form." It all depends on context.
What we can say is that if you said "good question" or "see this answer" and you did not supply an answer, then your motives are probably in the right place and you are probably making the site better.
Richard, when I use your google query from your comment:
site:stackoverflow.com "good question" "see my answer"
Then I actually find matches only from one single user doing this. So I don't know if your question should be a general question, or whether this one user is in fact trying to get some massive gold badge on the xslt tag...
This one user seems to be very proficient in XSLT after all, and I like his answers, which I previously appreciated for my own questions. Nevertheless, seeing that he does it virtually on every question he encounters, including praising the OP, which seems silly if every XSLT question is automatically a good question, then I agree, it's not really good form.