What I also can't get my head round. Why should Mastodon be anything other than what it wants to be when there are projects in the Fediverse that are not microblogs?
To begin with I'm not against such a proposal, do have accounts on mastodon instance that for example have 5k limit and consider that reasonable and better. At the same time I came from diaspora, and wasn't so much looking for microblogging. In any case I loved twitter with only 144 characters, that at least was a challenge. Also the display toot's up to ~500 characters entirely and than go to "see more" already creates a certain self restriction for toots.
That said, to a certain extent this request is just another nail in the coffin of the idea of a #fediVerse. Same as the intent to create a mega instance like #mastodonSocial. #Diaspora* and it's developers made the mistake to create such a death star, and the project kinda went down with it, beginning with changes in the code like skipping "likes" because of the burden on the server. Anyone who really is in favor of the main idea of the #fedi and #activitypub, and that is decentralization, should always consider any idea, proposal or request in terms of "what does this mean for the entire setup"?
We already had, again and again criticism by the community on #mastodon because it doesn't respect activitypub definitions or interprets them in an uncommon way. Only dominance in user numbers makes that possible.
Like to say, you only can say:
"I give a sh** on common agreements because I can allow me to do so".
Same goes for the centralization of the community onto one (or two) server, obviously showing off with the fact that the main problems and bottlenecks in social networks weren't understood. That's just a childish conservative expression of the view that "big is beautiful" and that you are successful if you become a big player. Nothing new and not even a mean criticism, we humans are as we are and are children of our time. So if someone is caught by the Zeitgeist and fashion of the moment, that's just what should be expected.
For me it's fine if mastodon has a 500 character limit and that it takes a little bit more of digging into the code to change that. In any case I'd consider it a problem if because of that an instance gets blocked by "the founding father".
We truly don't need any kind of benevolent dictator, and fostering and supporting any kind of hard or softfork of mastodon, as well as all the other projects out their, is way more important than fighting details of a project that's alive and well as it is. In that context, in any kind a true hardfork is creating incompatibility with the activitypub standards at that's what we really should be aware of.
Your comment Matthias, as well as mine, is in favor of the fediVerse, not mastodon, in favor of diversity not monoteims. And, I hate to bring it to you but, people are tribal, identify with brands and where raised social walled gardens, so the y expect "eierlegende Wollmilchsaue" and that, as of now, is the platform you are on, so .. let them be, we for our selves will always be on the side of those who reach out to create interoperability and understanding. That's how we tick.
:)
.. my few cents ..
New 
