Slugs are a bit of a problem. They like to crawl up into the leaves of my Hosta and chomp away until nothing is left. And the same goes for slugs written in many other languages. If you are Russian your slug is more likely to take the form 'forum-19'.
This is obviously an annoyance to Russian speakers who would like local language slugs and permalinks (although to be fair we don't really get any complaints… well just one or two) but will also be a major problem when tags make it into the wilds as tag slugs could end up completely empty.
I have been playing around with slugs recently and am proposing a return to the native WP 'sanitize-title' and the careful use of urlencode and urldecode to control things. In fact I am going to put this into 4.1 so we have plenty of testing time. There WILL BE PROBLEMS so please be patient. We should be able to deal with them one at a time.
Radio: Actually you could be a really great help here when this is done because you can test with a variety of languages……?
actually, they tend to display as unreadable chars for me…