Hidden links on ROR Wiki

Hello list members,

Today I noticed on
http://wiki.rubyonrails.com/rails/pages/WorkingProfessionallyWithRails
that there were a ton of spam links in the source code that I couldn’t
see on the page itself. Upon careful examination I found the links to
be hidden:

I am posting the content here for reference and to show patterns of
spam:

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This is really bad from search engine optimization post on view and
can lead to penalization of ethical sites that are linked from the
page.

How can we watch for this spam?
May be a filter is needed that checks for the existence of
“display:none”?
Or may be all links need to be converted to rel=“nofollow” which will
then not benefit any link on that page.
May be we need to make the wiki posts for registered users only.

Now I also suspect that such hidden links may exist throughout the
Wiki.

Frank

Rails Blog: http://railsruby.blogspot.com
MySQL Blog: http://mysqldatabaseadministration.blogspot.com
Linux / Security Blog: http://frankmash.blogspot.com