You can often fix it with `:syntax sync fromstart`, but Vim's syntax highlighting just keeps being a bit weird.

I usually just keep space bound along the lines of:

    :noremap <silent> <Space> :silent noh <Bar>echo<cr>:syn sync fromstart<cr>

This recalculates syntax highlighting as well as removes highlighting on search results/etc.

Basically, whenever stuff "looks weird", just mash space in normal mode and it fixes it. The fact that I have this bound to something like space should tell you how often I end up using it. :)

I recently gained a liking to search result highlighting, it's much more useful than I originally thought. The problem is not the highlighting itself but its persistence. I added a few autocmds to automatically hide it in certain events and a manual shortcut. Works better for me now, though it is annoying that `:noh` has some weird special status that makes it nonfunctional in autocmd.

I evaluated few plugins around this and this one I liked the most: https://github.com/romainl/vim-cool

I tend to avoid plugins for things that I can just do myself with a few keybindings or autocmds. I like that aspect of Vim (and Emacs) where the user is less reliant on plugins because there isn't really a clear, fixed boundary between configuration, scripting and external extensions. Though it comes with downsides (e.g. when plugin developers make the questionable decision of overriding user configuration).

I added 'autocmd BufEnter * syntax sync minlines=4000' to my .vimrc to make it buffer more of large files initially, so it gets less confused when you reopen a file and it resumes at a prior location deep inside and has no syntax highlighting.

I guess fromstart would work as well, but is probably best manually run like you do so a very large file doesn't bring the system to a halt.

That's why that happens, and a fix - thanks!