As a daily vim (editor) user, I had no idea that's what insert mode did in this context! I had never used it in vimium before. Thank you!!!
Yes, exactly. It also allows you to specify keys that it should ignore per site (so that the webapp always receive them), or even completely disable vimium for a site (or just specific pages on a site). By default, it's not active on gmail for example.
I thought that was what "insert mode" was used for. Hit i to go into insert mode, ESC to get out.