I see that too in Firefox on macOS, even with all blocking turned off. You can fix it with Vim’s ^L command (control-L: refresh display). I’ve had to do that i

I see that too in Firefox on macOS, even with all blocking turned off. You can fix it with Vim’s ^L command (control-L: refresh display). I’ve had to do that in the MacVim GUI occasionally too, especially when displaying symbols such as “→” that are wider than a normal character.