When I first joined the forums, I did feel the unneeded pressure to sub back. But when I later found out those messages on my wall weren't hidden I got quite angry, because they were plain advertising on my wall. And they almost never liked any episode barring a few individuals, so it was safe to say they didn't care for my comic.
I promptly unsubbed and put a note on my wall saying I don't do sub4sub. Furthermore, I delete all attempts to it, even if they are sneaky pm's.