Nothing wrong with how you feel about this, of course, but as someone who did that, less than an hour ago, let me explain why. ^_^
I usually do just comment on the post that contains the fic or art. I personally prefer to have all comments in one place, so wherever I post the content, that's where I want the comments, myself. But I'm the moderator of a new community, and I just posted a link on the community post instead of the content post (on the personal IJ) because I want people on the community to see me leading the interaction and feedback by example.
That said, I do completely understand why you feel that way. ^_~