If you break into the Horiningbrew Meadery it will bug a quest for the Thieves Guild, making it impossible to advance to further missions. Extremely frustrating.

I beat the Thieves Guild and never ran into a single bug.

I think he's talking about sequence-breaking.

As in, you visit Horining Meadery before you're supposed to. Ah well, either Bethesda will patch it or (more likely) players will make a mod to fix it/prevent it from happening.

I kind of expected bugs like these to happen. Earlier experience with Fallout. That's why i rarely enter/clear caves and so on before i get quests in them.
But i must admit it seems to happen a lot in Skyrim that quests bugs out because the player has already been in a place.