In post #4 of this thread the latex engine seems to go haywire halfway through a 'display math' section delimited by double dollars. The same code, with the PF-specific breakouts for in-line tex converted to latex standards, works perfectly in my offline latex engine. Further, to my surprise, when I pasted the PF-style latex code into a code window (lower down in the same post) that renders it correctly (I wasn't expecting it to attempt to render it at all!). Does anybody have any idea what's going wrong there? Also, it may be a useful observation for future reference that a code window renders latex, and seems to do so better than in the normal part of a post! EDIT: The problem is now solved, thanks to Samy and Ibix, so the problem is no longer visible in that post. It was where a superscript of a symbol within the latex code was the letter i enclosed within square brackets [...]. It was interpreting it as an instruction to start italics, rather than taking it literally as written.