Hi Adam,
I've been informed of an issue when inserting links using the tree drop down. I can replicate the problem on your test site.
Select 'P' as the break element.
Select a link from the tree drop down.
For some reason the link is inserted with a space for the text, rather than the description expected. This only happens if the cursor position is at the end of the editor, and if there is no text on that line.
Many Thanks,
Ady