Regarding self set reactions, that's fair enough; early days and all that!
It's not so much usernames I don't know but finding usernames that I sort of know!
With Lithium (if that's not a dirty word now!) you got a pretty comprehensive list as you typed following an @. You don't get that here. You initially get a list of those in the conversation then get a shortish list as you type but, as I said Alex's name never appeared anywhere in the list even when I got to ' alex_'.
By the way, I thought we weren't going to mention K**os here in an attempt to try to disconnect in people's minds the idea of using reactions as a means of getting more you know what!
Probably little hope but you never know...