It looks like Discourse forums don’t load if the character encoding is set to Windows-1251 for Russian.
To reproduce, set the character encoding to “Cyrillic (Windows-1251)” and visit the homepage of a forum. It will just be a blank page. There are error messages in the console that look something like this:
Uncaught SyntaxError: Invalid regular expression: /^[^A-Za-zГЂ-Г–Г-Г¶Гё-КёМЂ-Цђа Ђ-бїїв°Ђ-п¬њп·ѕ-п№Їп»Ѕ-пїї]*[Ц‘-Яїп¬ќ-п·Ѕп№°-п»ј]/: Range out of order in character class at new RegExp (<anonymous>)
(I’ve only tried it with two Discourse forums – Meta Discourse and my main forum.)