What are the rules for comma / other punctuation use in Russian? I've been noticing lots of differences –– you couldn't, for instance, write the above sentence with a comma in English. Also the comma in «Я думаю, что ... ».
Whenever a sentence consists of several clauses, they must be separated by a comma in Russian. Just like in these examples:
Тим молодой (clause 1), ему только двадцать (clause 2).
Я думаю (main clause), что ... (subordinate clause).