We are evaluating ArrowChat 4.2.1 on XenForo 2.3.3 and are seeing a bizarre result. All of the icons in the theme are getting duplicated. This happens even with the base Xenforo theme.
I had some time to spend on this. The problem is that Xenforo also uses the FontAwesome fonts, and this causes the Xenforo .fa* class names to collide with the names in ArrowChat. I fixed it by renaming the class names in the FA all.css file, and changing all of the class references in the ArrowChat code. It is not pretty, but it works.