Feature request: user-specific option for nick completer

[Mikaela]

Is your feature request related to a problem? Please describe.

I love the new reply syntax towards IRC, but I would love it even more if it would use a "," instead of ":" as I find "," more human in typing while ":" seems so robotic. Thus I would like to use "," instead of ":" when I reply to an user.

Describe the solution you'd like

As there are a lot of people who prefer ":" instead of "," when pinging people I would like to have an option with the appservice where SASL credentials are also configured.

Describe alternatives you've considered

Never using the reply feature and always typing everything by hand.

Additional context

A lot of IRC clients either default to "," or ":", but it's generally configurable and some may even use an emoji there.

The separator is what happens after the nickname in tab completion, in this case:

<Matrixian> IRCUser: nice

I would like to instead

<Matrixian> IRCUser, nice