When the page slug is generated from the post title, three icelandic letters are not converted correctly. These three letters are Ð ð, Þ þ and Æ æ. They should be converted to D d, TH th and AE ae but are not.
For instance, when I made a post with the title ‘Þátturinn’ the post-slug would become ‘þatturinn’ and when I tried to enter that address in my address bar it changed to ‘%c3%beatturinn’ and I got a ‘page not found’ error from Wordpress.
This can be fixed by adding the following six lines to formatting.txt, in the function remove_accents, inside the if (seems_utf8($string)) { condition.
chr(195).chr(144) => 'D',
chr(195).chr(176) => 'd',
chr(195).chr(158) => 'TH',
chr(195).chr(190) => 'th',
chr(195).chr(134) => 'AE',
chr(195).chr(166) => 'ae',
Also (from #5952)
When the post slug is generated from the post title, the letter 'Å' 'å' converts to 'a', should convert to 'aa' which is the general practice in countries using this character (Confer Wikipedia).
Furthermore, the Norwegian/Danish characters 'Æ' 'æ' and 'Ø' 'ø' should be converted to respectively 'ae' and 'oe'. As of now, these convert to '%c3%a6' and '%c3%b8'.
