I think it's a fine line between feeling guilty and feeling grateful. You're thankful for their comment/upvote, and want to pay them back in kind. Or, you're guilty because they commented/upvoted, but you didn't do the same for them.

I think you're right; it depends on how you feel, but it still doesn't change the fact that reciprocity is the result.

I've not had a curie in a good long time, so I know your pain there :)