Looking at the page sources, I don't see anything unusual in the character representation. If there were something like an embedded backspace character between the two characters, that might explain it, but I wouldn't expect it to happen TWICE. In other words, I can see it creeping into the thread title, and thus getting replicated to every subject line, but when people type "o/" in their messages, I wouldn't expect such a thing to creep in again.

So my bet is that it's with your browser's display. For instance, you may have a setting (or add-on module) which tries to display accented characters emulated in ASCII the way they were intended to be rendered. Compare, for instance, the way you have to encode accented characters in ABC, or the way that h is used in Irish and Esperanto to emulate, respectively, lenition (dotted consonants) and circumflexed consonants/u-breve.

In any case, I doubt the Mudcat input is wrong or that the behavior you see has anything to do with the "obscure Tech: threads" issues (by which I think Foolstroupe means the threads on how to enter non-ASCII characters safely). As for whether Mudcat should apply an explicit encoding to its messages, that's quite germane to those issues, but probably irrelevant to yours.