Malte,
I have seen a parameter in the recent OpenACS versions that offers to convert emails to display as an image file. Presumably any extra functionality could be added to whatever does that work.
Rather than mangle the email as it goes into the wiki, and rely on customised wiki forms, perhaps there would be a case for adding a 'hide email from spiders' parameter to the wiki application itself.
Another simple option might be to add some simple markup to enclose the email addresses to instruct the wiki to hide them. The issue with this is obvious in that it relies on the poster to add the markup.
R.
