• Have you checked if problem occurs with fish 2.4.0?
• Tried fish without third-party customizations (check sh -c 'env HOME=$(mktemp -d) fish')?

fish version installed (fish --version): 2.4.0

OS/terminal used: iTerm2 3.0.13

In #3696, I mentioned that the cursor does not blink in insert mode with fish_vi_cursor.

@faho was unable to find the documentation on blinking for iTerm2. Neovim handles this fine, so perhaps @justinmk knows.