Everyone has different needs. I run tech tutorials so I need:

(*) the entire post, not a excerpt and link to another platform

(*) long posts - posts need to be the size of stack overflow questions

(*) code blocks - it's a tech questions, posters need to be able to post code

(*) screenshots - posters need to be able to post pictures of what's wrong.

(*) serving a static site - I don't want to run a server so a script with an iframe is best. Though it would be nice if they had a message protocol for sizing.

(*) good a blocking/dealing with spam - it should be good at blocking spam. It should be easy to deal with 1000 spam messages should it ever happen. If I have to manually delete them one at a time then no.

(*) free - haha. the stuff I write is open source. I don't want to have to pay on top of my time.

(*) a sustainable business model - not sure what this means except my impression of things like giscus is they either require a server (see above), or they're running the service at a loss so it will probably eventually die.

(*) editable by mod - the posts need to be useful to other users and often posters mis-format

I don't use anything related to github because I expect github will eventually disallow this. I would consider using github if github itself offered the service. Github has one of the best UIs for tech question IMO. Markdown, drag and drop images, drag and drop video, large message size.

I use disqus because even though it sucks, it mostly checks all of those boxes. It's worst part is code blocks. It supports them but they are hard to use.

I looked into things like giscus and utterance. They both require a server or you trusting that they'll run theirs forever. They also use that ludicris "Act on your behalf" BS github permissions system.