It appears there is a bug in Nabble's code.
A entity (non-breaking space code) is inserted between each of the sub-forum names. This forces each following forum name to continue on the same line until it is forced to break by running out of space at the right end of the column. There is no such non-breaking space within forum names, so they will wrap.
It seems to be the reverse ought to be the case, so that complete forum names stay together.
Let's hope the Nabble team make the adjustment soon!
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.