Sorry, that's worse.
The problem is that there are already bona-fide % characters in the URL replacing space characters in the page title:
…/title/Re:%20Expect%20a%2015%%20performance%20loss%20coming%20soon
The fix to escape the % in "15%" also escapes all the others, with the result that the new page title has all the escapes in.
The only way I can think to fix this is to go back to the original and make a special case of a "%" that is not followed by a hexadecimal digit:
var urlfix=unescape(window.location.hash.substring(1));
urlfix = urlfix.replace(/%[^0-9A-Fa-f]/g, function myfunction(x) {return "%25"+x.slice(1);})
(Warning: I have made it a career ambition never to learn Javascript.)
That will lead to odd behaviour when the % is followed by a digit, but I can't see an obvious solution.
On reflection, I think this is a Wikidot problem. I've filed a bug report there: http://feedback.wikidot.com/bug:1152
