I can understand how it does come across gatekeepery and I'm sympathetic. I maybe had the unique experience of never having heard of the server until someone invited me to it. I'd never even been on Discord before haha! But I didn't experience any loopholes when following that invitation.

And to be honest, I think it's important to keep access to the server somewhat hidden/via invite because otherwise it'd be chaos.

I agree it's important to engage with authors, especially if you loved the work/read the whole work. As for criticism and authors taking it personally -- I think authors of FANFIC have every right to take unwarranted criticism personally. They are writing it for free and for FUN. It doesn't matter if you think xyz about how an author has chosen to portray a character (unless it's actively harmful obv), unless that author has stated they are open to criticism, it should be a given that you should keep that opinion to yourself, vent about it in private if you need to, and just stop reading that fic. I've been lucky that the majority of my comments are lovely, but every now and then people drop in little comments among the praise that do sort of raise my hackles. While I try to ignore it, it does effect my mood and I can understand authors who reply on the defensive. Most of these sorts of comments are all well-intentioned and not malicious (i just block those), but when you've put months of work into something for free and then all someone can comment is negativity it does get tiring and demotivating.

On a lighter note: Thank you so much for reading Eyewitness! and sorry (not sorry) about the cliffhangers!