I'm a really light sleeper and I choose to not stay in shared rooms because I could never sleep and it would really affect my holidays. I think if you stay in shared rooms you have to expect noise. I get there is etiquette like being quiet if your coming in late, not turning the lights on when everyones asleep etc. But I think its unreasonable to get annoyed at someone for snoring because its not their fault. Its not like your deliberately trying to be inconsiderate. I think its really lovely that you are concerned though. It seems like you are very thoughtful and considerate of your actions which makes you a far better guest then others I have come across in hostels.