Cannot remove spelling error highlight from lowercase "vim"

Question

The word "vim" is flagged as a spelling error in my documents. If I capitalize it, the error goes away.

I don't want to capitalize "vim". Adding it to dictionary with zG or zg does not help.

UPDATE

OK, I've discovered this word was somehow flagged as a "rare" word. How do I remove that designation? I'm not using any rare word list as far as I know. There's none in .vim/spell.

UPDATE 2

If I remove my spell dir, "vim" is still getting flagged as rare. Where could the designation as "rare" be coming from?

UPDATE 3

OK, this is officially driving me crazy. I moved the spell directory and did vim -u NONE and it **still* shows up as a rare word.

UPDATE 4

OK, tracked this down to neovim. I don't know why, but the en.utf-8.spl file is in the /usr/local/share/nvim/runtime/spell directory is getting loaded. How do I make changes to this file?

UPDATE 5

OK, so I ended up copying over the en.utf-8.spl from the vim install into neovim. But if someone could explain exactly what was happening, I'd appreciate it. How did this word get marked as flagged in the neovim spell file in the first place?

Answer 1

Check if this is caused by 'vim' is being used at the beginning of a sentence.
In my tests on vim 8.* only the first 'vim' of "vim vim vim" is flagged as a spelling error.