There are two ways to get accented characters onto an html page.
The wrong way is to enter a character code directly from your keyboard. For example, here's character %E9:
éNow, that may look like this ...
... on your PC, but different computers use different character codes, so on a Mac it'll look like this ...

... and by the time it's printed it'll probably be just a letter i.
So, what's the solution? How can we all end up typing in harmony?
Well, the answer is to use html entities. Entities start with an amperstand (&), have the name of the character in the middle, and end with a semi-colon (;).
So, the proper way to get an e-acute in html is to use the entity é
But that's where we hit a hiccup in 'Tavi!
If you enter é 'Tavi displays it exactly as you typed it.
There are two possible solutions:
1. 'Tavi should spot that it's an html entity, and pass it through unchanged. (If a user actually wanted to display é, she would enter é).
2. 'Tavi should spot the character code that corresponds to an entity, and output as an html entity. This is much more Wiki-like behaviour (i.e. you just type, and it works). However, as already explained, %E9 -> é on a PC, but Î on a Mac.
Interestingly, if you enter a name in preferences using an entity, Tavi correctly says "Your user name is ..." when editing a page, but incorrectly shows the username in the document, which means I now have three homepages:
http://tavi.sourceforge.net/index.php?page=Sean+D.+Soll%26amp%3Beacute%3B
http://tavi.sourceforge.net/index.php?page=Sean+D.+Soll%26amp%3Beacute%3B