IE for example don't want to render the RDF file with those characters. I made a simple hack(?) to fix this problem:
copy the ent.dtd file from here, transfer that file into your weblog directory and add the following line into the RSS 1.0 Index template (after <?xml version="1.0"?>):
CODE
<!DOCTYPE MOVABLETYPE SYSTEM "ent.dtd">
But i don't know how to convert some of the special characters in other templates without destroying HTML-tags.
Hope it's understandable.
Thanks