It would be more accurate to say that special characters are supported irregularly in BM.
Unfortunately, getting a PHP/Apache/MySQL stack to properly support Unicode is an absurdly fiddly business, and most of the settings involved in it can only be changed by Tom (they're nothing to do with the actual code, but rather the server configuration itself).
If it were up to me, I would spend a week fiddling with everything until Unicode worked properly, because dammit, this is 2017, and we should be able to support it. But as things stand, I'm not going to try and ride Tom to get it to work when the next point update of any of the systems involved will probably break it again, especially since he's known about this issue for the past 16 years and chosen not to do anything about it, even though his native language actually requires some of those special characters.
Sorry.