To my knowledge, there have been few (and not very successful) efforts to develop a common standard for wiki markup. I wonder whether this the cause or the effect (or maybe both) of the particular evolutionary landscape of wikis (which displays a lot of redundancy).

The lack of a common wiki language might be regrettable for the end user, who needs to pick up the best features from the available engines without sacrificing portability. But I'm reluctant to think that there was no successful standardization project for wiki markup so far only because developers follow some sort of "lock-in" strategies.

IMO the babel of wiki dialects is the price (?) to pay for the richness and diversity of wikis, which makes specific engines closer to one's taste or more suitable than others for specific kinds of application/target users. Wikis, as far as I understand them, are an interesting effort to attain simplicity through a more friendly markup than standard markup languages. And there is no common agreement on simplicity. If standardization was the main concern, we would probably use textareas with raw HTML and give up our wikis

Textile (http://textism.com/tools/textile/) is considered by some as a kind of markup standardization initiative, although - considering the relatively small number of wiki engines that support it - I'd tend to consider it just a (brilliant) marketing strategy to sell an arbitrary markup as simpler or more intuitive than most wiki markups.

If you are interested in serious standardization projects, though, you will easily find different initiatives online, including (but not limited to) the following:

Wiki Markup Standard
http://www.usemod.com/cgi-bin/mb.pl?WikiMarkupStandard

Inter Wiki Markup Language (IWML)
A Common Interchange Syntax for Wiki
http://www.altheim.com/specs/iwml/

Just an small addition. Here is what I recently wrote in an email concerning the creation of a Markup Standard:

I'm not really conviced my self of such a standard. It sounds nice in
theory but it's hard to make. You would have a hard time to convert the
whole Wikipedia to a new syntax. And you would have a hard time to
convince me to give up the (in my opinion) simpler and more intuitive
syntax of DokuWiki - and I'm not the only one to be convinced.

I think a much more useful thing to develop would be a standard exchange
format (eg. a XML format). I think there are some proposals for such a
standard flying around somewhere at the mediawiki servers.

Andi