Nope. Plain text only, I believe.
The big question is: Why not?!
This is a little silly.
With groups set up, you could effectively replace old school “forums” with the more dynamic “groups”.
You can just message from your profile, or to a group. It turns the entire site into an extendable forum. All that’s missing is a better text editor.
This would simplify things a great deal. Right now, you can start a conversation in the forum; in a group; or just with a message from the profile. These are not all that integrated. Way too easy to get lost, or lose related content. It’s a mess.
I know with the new updates, bbpress and BuddyPress are friends, and you can (in theory) feed your group forums into the site wide forum. But… why have a site wide forum when you can just message to groups?
I’ve had to create a page on the site just to explain to people what this Groups vs Forums stuff is about. Think about it from their perspective. What the hell is a “group”. This really smacks of developer centric thinking dominating user centric thinking.
I’ve found this: https://wordpress.org/extend/plugins/bp-tinymce/
But I’m getting a fatal error, and so are other people (https://wordpress.org/support/topic/plugin-bp-tinymce-fatal-error?replies=3#post-4107216)