set matchpairs+=<:> and
set comments=…; this is okay for actual html, but php.vim doesn’t restore these settings, so you get error bells when writing
$foo->bar() from the unbalanced ‘>’, and you can’t format your PHP comments anymore because they’re completely unrecognized.)
Anyway, this led to the realization that my vim setup, as large as it is growing, is built on a large batch of external code, which is in turn dependent on both vim version and the distribution. Due to subtle changes to hundreds of defaults—especially complex values like the aforementioned matchpairs and comments settings—it’s impractical to predict how a given vimrc will behave in a random environment.
Thanks to site-lisp, I am guessing that emacs has essentially the same issue: your initialization may interact in with site-lisp code to produce per-host variation in behavior.
For something I’m going to spend my day in, that’s a painful situation. The variation interrupts the flow of expected results, pushing the editor back up into my consciousness. But would I want an editor I couldn’t customize?