Not mentioned in the thread above. Do you fully support rtl languages like Arabic and Hebrew? ( meaning everything goes from the right to the left including all styles, pop ups, menus ). This was a pain point for me in many different platforms.. only one really nailed it from the start.
Yes, xenforo supported RTL from the beginning my client's site was one of the first that migrated to xenforo with no big problems. At the beginning we had to make some tweaks but xenforo now support RTL in the core system. You can choice this in the language setting. if you need any further assistance just let us know