"But why do not you vote on posting but rather comment on it? I would like to know if there are special reasons. I would like to know if there is something deep meaningful." - this is key. I think if they are upvoting other people's comments they may have simply forgot to upvote the post. 

I will occasionally upvote comments on my posts if I feel the discussion is important.

I wonder if this comment will get an upvote?? 🧐