I really don't think it's ethical to take an "I will use carrots and sticks" approach to interacting with people. I don't like it when fanfic writers try to armtwist or guilt anyone into commenting, but I'm just as unamused when readers act like having written and posted anything entitles them to push for longfic or finished-fic.

My larger complaint with this kind of behavior is that, one, if I let it, it would also make me mistrust positive feedback. I want people to interact with me over a story on account of having something to say about what I offered freely; not to try to manipulate me into keeping up the good work. And two, fandom thrives on the mindset of offering what you can freely and expecting it will reach people who will want it. Fandom struggles when too many people feel like they're not good enough to write and create, and if they do anything, people will berate them for not being better.

So many longfic writers started out as shortfic and oneshot and unfinished-plotbunny-that-would-not-leave-me-alone-but-really-should-have-picked-someone-more-experienced-because-I-can't-do-it-justice writers. You're making it harder for them to perservere and hone their skills, when you behave like this.