Nick completer in WeeChat 2.4 no longer add spaces by default
February 28, 2019
With the beginning of WeeChat 2.4 (released 2019-02-17) a space is no longer automatically added when you complete a nick at the beginning of command line.
This leaves you with Hund:_ and not Hund: _. If you want the old behaviour back like me, the solution is simple. You just need to change one simple setting:
/set weechat.completion.nick_completer ": "
Don’t forge to save the changes with /save.
Source: https://weechat.org/files/releasenotes/ReleaseNotes-devel.html#v2.4_nick_completer.