As you've already noted, only answers can be accepted. Comments are considered transitory and therefore doesn't have this option. You can upvote a comment, but not "accept it as an answer." If you feel that a comment answered your question, here are a number of steps you can follow (in order of preference):
Add a comment pinging that specific individual (using an @-mention) and request them to write up an answer. Once an answer is written you can proceed with the usual voting behaviour.
If there's no response from the commenter after some time, write up your own answer (possibly as a community wiki) referencing the original comment/er (as a form of recognition). Again, from here, you can proceed with the usual voting behaviour.