PM replies via the forum fail if a username contains a comma

[computezrmle]

Describe the bug

Got a PM via the LHC@home BOINC forum from a user with a username like this:
aaa, bbb

At the standard reply form the address becomes numeric_user_id (aaa, bbb) which when sent fails with a server message like:
Can't find user bbb

User lists like 123 (user1), 436 (user2) usually work fine.

It is obviously the "," inside the parentheses that irritates the server.

Please look into it and allow usernames of the form aaa, bbb.

Steps to reproduce

No response

Expected behavior

No response

Screenshots

No response

System information

No response

Additional context

No response

[AenBleidd]

This should have been fixed via #5710.
@lfield, is there any chance you can have this patch tested to verify it solves the reported issue?