I disabled the tidy engine on wikimedia server tonight. It was causing some weird trouble with the cluster, eventually rendering it useless.
So now that tidy is disabled, pages are no more automaticly fixed and all wikipedians should fix their broken HTML / wikisyntax :o)
The good news is that the site is back up \O/
Update nov 14th 22:45 UTC: Someone wrote a guide to help everyone fix their signatures http://en.wikipedia.org/wiki/Wikipedia:How_to_fix_your_signature