'@@[username]' to reply to last message by user
When replying to users, an individual is required to remove their hand from the keyboard to the mouse to click on the message of the user.
For a smoother replying experience, more in-line with the current practice of using '@', I would suggest offering '@@[user]' to reply to the thread containing the last message of that user. If there is no last message, this would default to '@' behaviour.
This update would improve accessibility for users that have difficulty using a mouse and also facilitates ease-of-use for those without accessibility requirements. Overall I believe this would improve the utility of, and experience in using, the chat reply feature.
I like the chat replies feature, it has the potential to make moderating easier by providing better context to messages.
Currently however, I do not believe the feature offers a comfortable keyboard-only way to reply, and so it risks being under-utilised.