One of the bugs was straightforward. The timer function of
eglot--update-hints must set the correct buffer.
The other is much more odd. When using Eglot on Emacs's own
src/coding.c, the jit-lock code starts calling its jit-functions over
and over again with the same sequence of arguments, like so:
This continues forever at a very fast rate and saturates the LSP
channel.
At first I thought that it was because eglot--update-hints-1 is
actually causing the buffer to be modified with overlays sometime in
the future, but it is not so! It seems that merely calling