I don't agree with your reading of Thiago's tone--you found it patronising, I found it trying hard to be polite to Bram, who's being the same dismissive senior dev he was when he rejected Thiago's first and second attempts at patches to do what was done very well in neovim.
As for why vim should care? Because at this point I'd put money on neovim as the long term winner, and if I were Bram, I'd worry about vim joining vi on the sidelines as 'still developed, still in use, but not the vi everyone uses when they log into a linux box'. I'd look at my codebase and neovim's, at my toolchain and neovim's, at my community and neovim's, at my velocity and neovim's, and I'd imagine neovim eclipsing vim over time.
Maybe that's fine. But Bram is hardly some god-king who's position as foremost developer in the vi universe is a lifetime appointment--especially after he took that position from Bill Joy.
Why are you on the side of someone who has a hard time being polite. I read the original threads about Thiagos original patch and he was in the wrong. He ignored issues that were outlined and it was clear the patch was not ready. He was not polite.
Once again Bram brings up a valid issue with neovims design about using msgpack for RPC. It just adds another layer of difficulty.
So explain to me why vim should include such an obviously flawed design?
By "trying hard to be polite", I mean he was making an effort to be polite when he had no need to be after Bram was already rude and dismissive, not that Thiago has trouble being polite. Read the neovim issues in github: Thiago is a model of good-natured engagement with almost everyone. In the original patch request thread he's far from impolite, and he's more polite than Bram is.
And "makes debugging difficult" is an observation, not a criticism or valid reason to reject--it's certainly not detailed, as you said. Yes, it's more difficult debugging it directly, but the architectural separation makes the components more loosely coupled and more easily tested in isolation--it's a valid tradeoff, and one the neovim has demonstrated to work well in actual fact.
I mean, it's an accomplishment for Bram to add async to vim, but let's not forget who actually did it first, successfully, and along the way accomplished a lot more.
Why are you so hostile to neovim? By any measure they've done a tremendous job modernizing the codebase for vim and rejuvenating development of both neovim and vim.
Step back and ask yourself: if you were approaching both projects fresh, and asking which you might want to participate in, which would you choose and why, ignoring politeness on either side?
As for why vim should care? Because at this point I'd put money on neovim as the long term winner, and if I were Bram, I'd worry about vim joining vi on the sidelines as 'still developed, still in use, but not the vi everyone uses when they log into a linux box'. I'd look at my codebase and neovim's, at my toolchain and neovim's, at my community and neovim's, at my velocity and neovim's, and I'd imagine neovim eclipsing vim over time.
Maybe that's fine. But Bram is hardly some god-king who's position as foremost developer in the vi universe is a lifetime appointment--especially after he took that position from Bill Joy.