As Vim9 comes alive, and Neovim community focuses on Lua plugins instead, it seems this release is finally the update that will put a hard branch on the two communities. Up until now, most plugins (except Lua-only ones of course) have worked in both editors, but it doesn't seem like Vim9 will be supported in Neovim, so I guess what people go with now, will decide what you might stick with in the future (unless you're eager to switch development environments).
Although I am currently tip-toeing on NeoVim, I still feel this is a horrible break-up.
Yes, Open Source simply allows you to branch whenever you're unhappy with the original but this comes at a cost for the community. The cost of having two diverging programs to deal with.
In this case, the motivation was simply insufficient. Some people wanted vimscript+lua instead of vimscript. They felt the code was too difficult. They wanted to develop on their own.
Not bad reasons in itself, but does it weigh against the tremendous cost for the community of the split? Isn't a split only justified in situation like OpenOffice/LibreOffice when there is no other choice? Couldn't they not convince Bram Moolenaar of proposed changes, and if not, doesn't this have a good reason.
I hate NeoVim for the reason they've split, even though I understand it might become even better than Vim in the long run. You need better reasons to fork and divide an ecosystem.
I think Neovim had a whole bunch of other reasons to split. I'm pretty sure that Neovim's server mode, which allows it to be used with other editor frontends, is simply not present in vim. For me this is the whole reason to use Neovim. But I think it also natively supports tree sitter and/or LSPs, which really improve the coding experience.
Anyway iirc Neovim wanted these features integrated into Vim itself and only started a separate project when it became clear that that wasn't going to happen. My understanding was that at the time Bram was hostile to lots of the changes that people wanted integrated. You can read some of the discussion [here](https://news.ycombinator.com/item?id=14245705) and [here](https://news.ycombinator.com/item?id=7287668)
And when Bram did finally add async support rather than take the neovim work and us that he did it in a specifically non compatible way. I don't know the ins and outs but as an observer that does come across as a little petty.
Well, Bram is the author of the parent project, he doesn't have any obligation to make it compatible with the derivative.
Vim has been around long enough that I'd argue it's just as much owned by the community at this point.