I will repost what seems to be the current policy of all SE from an answer which someone stole from a comment by Jeff Atwood:
Steal comments that answer the question and post them as an answer. If it happens enough either the misguided commentators will
be annoyed enough at the "lost" rep to give outright answers next
time, or no one will notice / care and you'll help the community
and... oh yeah, get some rep.
BTW, I stole this answer from Jeff Atwood's comment on sysadmin1138's
post, so you should upvote this to annoy Jeff (and I stole it from you
As Nixphoe points out in the comments below, sometimes you have to
lead the author along to get more information out of him. In those
cases, comments should be avoided like the plague and any information
discovered in comments should be placed in either the original
question or in an answer.
If you post an answer based on limited information, wait to see if
more info is given and then edit the answer accordingly. It's also
nice to modify the original question to include all information that
is garnered in the process.
Throughout all of it, encourage the author to update their own
question and provide more information. Eventually people will get the
hang of it. The Q/A nature of the site is defeated if half of the
pertinent information is in comments, and the accepted answer is only
truly acceptable after reading two dozen comments strung out over the
question and three different answers.
Always under all circumstances strive to keep all information in either the Q or the A.
I agree with this. Also, remember that SE doesn't even care if you accept an answer:
Accepting an answer is not meant to be a definitive and final statement indicating that the question has now been answered perfectly. Heck, we don’t even expect people asking questions to come back and accept an answer most of the time.
emphasis changed by me