Never heard of those particular files - but I never heard of hosting that didn't allow .txt files, either. If they are in a format that can be read and edited in Notepad, they are normal text files and you shouldn't have any problems.
(If you are using a program made by somebody who thinks it sane to use the .txt extension for a new kind of file, better try to find out what more is wrong with the program before depending on it)
