There's meta about Blaine saying Kurt's "fey boy tie" was his kryptonite. There's a group called the Feyboy Collective, so some people on Tumblr said. Kurt is a fey boy. Obviously Blaine approves of Kurt being fey. For me, "fey" means fairy in the mythical creatures sense, which was not what Blaine meant, or has meanings of gay with implications that are kinder than saying "effeminate." I tend to think it was "Feyboy," though. The Powers That Be are very familiar with gay culture. No one who knew the clothing that's symbolic of a leather Dom thought it was an accident that Blaine was wearing that cap. It wasn't accidental that Blaine was moving his arms and finger like that in the dressing room in the "Diva" song. Blaine was experimenting with clothing styles and mannerisms that would make it visible that he's gay.
You Gotta Let It Out has much about the significance of duets and meanings of lyrics. Kurt and Blaine were totally in sync in their duet, with lyrics of "just can't get enough." Tina understood it. It wasn't like what Tina said about what she saw it as was subtle. It wasn't like Blaine was subtle about what it meant that he and Kurt had had sex. I'm still interested in Blaine saying they were together at Christmas, too. That could definitely be taken in a sexual sense. The characters spelled out what the duet was and Blaine said what he thought having sex meant about his and Kurt's relationship.
In "We've Got Tonite," Kurt got the "I know it's late and I know you're weary" line and Blaine got "I know your plans don't include me." Blaine sang that just before Kurt pulled him into a hotel room by his tie. Kurt obviously had plans for Blaine in the immediate future. I'm actually cool with Kurt and Blaine being best friends who have sex with each other, but it's clearly going to be more than that again, especially considering that Blaine is in love with Kurt. Kurt didn't convince anyone when he said he and Blaine were "just friends." It's going to happen on Kurt's timeline, though.
I'd heard various spoilers, but I tried not to get my hopes up. Things for Kurt and Blaine in "I Do" far exceeded my hopes. I'm sure there will be more drama. Indications of where things are going seemed clear enough, though.