There's a problem with the way the word filters replace text. They seem to only replace whole words. I want to use the filter to replace all instances of ae with ä, but it will not recognise ae unless I leave white space on either side, or make the search text *ae*, in which case, it deletes all text in the word containing ae besides ae, and replaces that with ä. I realise that changing this could result in problems with mismatches, but you should probably rely on users being smart enough to choose terms that are unambiguous enough to not be picked up accidentally.

Maybe you could let it replace *ae* with *ä*... Don't know if it would work though

Edit: Nope, it just replaces it with *ä*.