MuEdit does not work with double-byte characters, and cannot handle Chinese, Japanese, and Korean documents. But it has been successfully used with single-byte foreign scripts, such as Arabic and Hebrew.
Pictures cannot be pasted into documents.
Mac’s Styled TextEdit routines are quite slow. You may find MuEdit rather sluggish for documents over about 15K characters.
Dialogs cannot display characters in a font which does not use the system script. For example, Find and Replacement strings will appear as garbage characters if not in the system script. But they will be used properly nevertheless. You may like to use Copy/Paste to transfer strings into the Find Dialog from a text window where you can see them.