I sometimes check the users other comments if I have my doubts. But I usually check out every person who has bothered to comment on my posts. Even if it's a generic "nice". In the end I follow people that offer some interest to me and there aren't that many.

I comment very briefly too if I just don't have anything smart to say or add to a topic. Showing some support is still good.

I don't think it's a problem. We have the "mute" button for extreme cases.