Hmm..well all the languages that are written using the same alphabets as in English (a-z,A-Z,0-9 etc) are just the same as English (software can't say, without explicit programming, tell what language it is, if the words use same letters that english does). Like "software" means just about the same to the program as "fdsafds" since they consist of the same kinds of alphabets. Problems that may occur, occur probably with languages that use scandinavian letters ä, ö or å, or languages that use different "alphabets" (different tags) like china.
Probably the biggest problems can be solved by making sure that the machine/software that processes the data has the locales it needs (all the locales you think the input may need). I'm not completely sure what MySQL does if you try to save some chinese tags into a MySQL database (an example), but try out and you'll see