Here’s an article on how to create custom BuddyPress slugs. Perhaps this will help: https://buddypress.org/blog/how-to/customizable-slugs-in-buddypress/
@Jeff, you’re not getting the point. It’s not about custom BP slugs.
This permalink (or post slug) problem is something I hate about WordPress not being friendly to international users. Unlike wikipedia or amazon, WordPress seems to have a character limitation when used other than English, like Hindi or Asian characters.
So to answer your question @slicktig1, the only possible solution at this moment is to edit each by each through phpmyadmin. However with some hacks you should be able to edit category slugs if you search wpmu forum.
On group slugs, this is bp function, so not sure if the same wpmu hack applies or not. But at least there should be an alternative method to use postid than postname. (This is something we have to ask core developers).
@socialpreneur
You were correct. I did not understand the issue. Thanks for enlightening me.
This is why providing examples is always a good idea!