I just double-checked this. I'm a Moderator, and ...
When editing my own message, I still see the toolbar.
When editing someone else's message, even if it's another Moderator's message, the toolbar is greyed-out and missing all buttons.
Was this intentional? If it is, why?
When editing someone else's message, I can't even use ctrl-key shortcuts (such as ctrl-B, ctrl-I, ctrl-U) to affect any formatting of the text. Indeed, ctrl-U opens up a rather large HTML page in a new tab, rather than underlining the highlighted text. (Did Groups.io do that, or is it Chrome intercepting ctrl-U in that case?)
Andy