Ctrl-i in gmail textarea is usuable...

[mercutiomontague]

Pressing Ctrl-i in Gmail's "standard view" invokes gvim with alot (possibly all) html from page. In GMails' "HMTL view", this feature works correctly and only the textarea text is edited in GVim.

[gkatsev]

This is because gmail updated how they handled text boxes. There might be some stuff we can do to make it better but it's on the backburner because there are other issues that need to be fixed and there are not many developer resources on this project.
PRs encouraged :)

[for-coursera]

...Just in case you need some additional voices saying we are dying being unable to use Vim with email :)

[jstetten]

If you press Ctrl-t in textarea boxes (including Gmail compose), you will get some of the most common vim commands (including visual mode).

Hit Ctrl-t again to toggle modes.