Nice work!
I don't know, what you're intending to do with this, but I'd suggest
two features anyway:
(1) Professional quality output for print, IMHO best using conversion
to LaTeX and then pdflatex. This
is easiest to add, while the markup is still simple (it would be
rather impossible by now for MediaWiki
which allows so much HTML+CSS), and while incremental adding features,
you can always
have the requirements of conversion to LaTeX in mind.
(2) Math: Any serious article in mathematics, physics etc need
formulas. You can provide support
for formulas without much to do on the server side using jsMath[1],
and as the formula source is in
LaTeX you can directly feed it to step (1).
Regards,
Peter
P.S. Please note that it would be better to have a backlink to
Wikipedia, a mentioning and
on-line copy of the GFDL and not to have the Wikimedia logo on your site.
[1] http://www.math.union.edu/~dpvc/jsmath/ "jsMath: A Method of
Including Mathematics in Web Pages"

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