Emphasis syntax is still somehow broken. URLs like "svn://example.com/foo/bar" open an emphasis. Garbage like "abc //bar def" opens an emphasis. Garbage like "abc //http:// def" opens an emphasis with "http:// def" as content. See test cases. Adding two backslashes to the parsing regex lookahead (what would be "//(?=[^\x00]*[^:])//") breaks emphasised strings ending in colons ("//Now comes important stuff:// Explanation").
Old bugs related to emphasis: http://bugs.splitbrain.org/index.php?string=Emphasis&project=1&search_name=&search_in_comments=1&search_in_details=1&status=&do=index
I think we have to run a more sophisticated regex looking for more valid URLs, for example (simplified without the unicode stuff) "((<=(\W:)|(.[^:]))//)|//(?=\W))(?=.*(((\W:)|(.[^:]))//|//(?=\W)))".