A public chat has been created for the Nextcloud community. If you are a translator at Transifex, or you want to report a translation error, please also notify us on it. Or maybe you want to talk to a group of translators?
Link: Translations l10n i18n 
Actually only two persons are there.
Downside of the mentioned chat is that you cannot create an account yourself.
You need someone inviting you from Nextcloud GmbH.
I would vote for staying here in the forums.
Maybe both systems can be combined in the future.
But you can write as a guest. You can always leave a message 
.
I am also staying on the forum.
Chat can be used to leave a short note about a problem. There are users who find a translation error but do not want to register on the forum. And this chat is supposed to help them.
In addition, translators may leave some general comments on, for example, the operation of Tranifex or the text strings of a given application (in general).
it looks like a talk-page…