Does hi link XXX Normal provide any benefits? For example the syntax file included by default syntax/vim.vim includes the line:
hi def link vimUserFunc Normal
This often conflicts with CursorLine highlighting since Normal often sets a different background color than CursorLine e.g.
hi Normal guifg=#ffffff guibg=#000000
hi CursorLine guibg=#111111
Removing the link does not seem to have any immediately obvious adverse effects.
Are there any benefits that I am not aware of?
Without a highlight, it could be highlighted by a different syntax group that might contain it. My guess is that vimUserFunc was meant to look like normal text so it wouldn't be highlighted like built-in functions.
If by removing it, you mean deleting the line in $VIMRUNTIME/syntax/vim.vim, you shouldn't. You can clear it with :highlight clear vimUserFunc in a script like after/syntax/vim.vim. I doubt this will be the only occurrence of this, though.
This often conflicts with CursorLine highlighting since Normal often sets a different background color than CursorLine e.g.
Getting CursorLine to look "right" is an uphill battle. By default Normal isn't set. Most of the stock themes don't actually set a background for anything unless its meant to stand out (e.g. Error, Search, etc.), in which case, inconsistency with the CursorLine background shouldn't be a concern.
If anything, setting a background color on Normal is creating your issue.
