There is a little-known feature where, if you have verified a user (eg, via the
emoji game), then when you mouse-over a message that they sent, it gets a green
highlight.
We also show a brown bar sometimes, and according to the CSS there may be a
yellow bar too?
Very few people seem to know this exists, and even if you do know it exists
nobody seems to understand what exactly the various colours are supposed to be.
So, rather than porting this magic mystery feature to Rust Crypto, let's rip it
out.