Recently on SO, a question asker asked me a yes/no question in the comments. I wanted to say "yes", but I had nothing else to add. However, the comment length filter required me to add characters, so I added what's essentially filler text to my "yes" comment.
With an experienced user, I might just upvote the comment and they would know what that meant. A lot of times with clarifications, you might say "yes" and that's sufficient, but with a "no", usually it's "no, here's why ...", so the comment length filter isn't a problem.
In this situation in the future:
- Yes with filler, e.g. ("So you mean I should do X?" "Yes" -> "Yes, you should do X")
- Upvote the question comment
Edit: Hmm, it seems that filler in comments is common practice