What happens if I answered a question, the questioner says "thanks, fixed my issue" in a comment, but didn't mark the answer as correct?
Not sure about the etiquette or process. Can anyone clarify?
If the user is relatively new and has never accepted answers before, then it's often just innocent ignorance of how the system works. That the user has posted positive feedback that your answer has helped in solving the problem is already a great first step. I usually comment back like:
You're welcome. Since you're new here, please don't forget to mark the answer accepted which helped most in solving the problem. See also How does accepting an answer work?
Note that you should not explicitly mention your own answer ("this answer", "my answer"), for sure not if there are more other answers on the same question. This can otherwise be interpreted as nagging. It's important to formulate the comment as neutral and purely informative as possible ("the answer"). Again, note that you shouldn't post this comment as long as the user hasn't provided any positive feedback.
It works for me in many cases. If the user has a history of questions with answers which seem to have solved the problem, but are yet unaccepted, then I often add something like the following to the comment:
Also, please don't forget to do the same for questions which you asked previously, whenever applicable. You can find them in your profile. If no answer is applicable and you have already solved the problem by yourself, then you're eligible to post it as an answer and accept it.
Don't forget to take into account that the user can only accept an answer at earliest 15 minutes after the question is been posted. Maybe the user want to, but simply can't yet. Just wait some time before commenting.
But if the user has already accepted answers before according their question history and thus already knows how the system works, then just ignore it and let it go. It would otherwise be interpreted as nagging. Post at most a "You're welcome." comment which fits nicely in 15 characters :)
You go have a cup of tea. Things happen. This is one of them. If you keep on creating good questions and answers, you will not lack for rep, whether or not some particular OP ever accepts some particular answer.