hello and fanx for information .
I still don't have time to take a look at moodle-wiki :\, but what about diffs ?
as much as I know,
* HtmlArea produces one-line html code (or similar - hardly readable by human )
* and diffs in wiki are counted on per-line basis
* HtmlTidy arranges html nicely, so diffs would be human understanable.
ps.: HtmlTidy extention will be by default in PHP5
I believe in PowerOfWiki :D