At the very least there should be some warning if different versions of fonts are being used at different stages, but I suppose this could get very noisy with the common practice of having at least 3 very different fonts all claiming to be Helvetica-Italic, so perhaps it needs to be added to some list of debugging flags and left off by default.
Noisy is good. A user should be informed about all possible errors, and using a font that the user may not have indicated certainly violates the idea that TeX source compiles identically on every machine it's run on. Of course, operating system limitations such as the inability to concurrently install different versions of the same font cannot be detected, and the current implementations don't allow us to specify which font version number should be used, but aside from that, if TeX sees three fonts, it definitely needs to go "ZOMG MY OMG! You are in a world of font hell if I don't tell you about this" =)
- Mike "Pomax" Kamermans nihongoresources.com -------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex
