I'm aware of this question, but that one is about a flag for answers instead of for comments.
I've seen some answers from newbies that get answered, and then instead of marking the answers as Accepted, they post a
Thanks that worked!
comment under the answer.
I always post a comment:
@somenewbie If this answer solved your question, please click the checkmark next to it.
then, but they never react.
Why this is a problem:
- It is unfair for the answerer, because he/she doesn't get his/her 15 reputation and eventually a badge
- It makes it more difficult for future visitors to find a solution
- It's just generally confusing. Someone not reading the comments could attempt to help again while the question is already solved
- They stay in the Unaswered section
- In beta sites, the answered rate unjustly lowers
So, I think it's a good idea to add a "Should be an Accept" flag for comments, that can be used for comments where it's totally obvious that these should be an accept instead of a comment (and thus that if the asker knew how SE worked he/she would have accepted the answer).
Then, if the flag is valid, a moderator can delete the comment and make the answer marked as accepted.