Albus strolled through the corridors with his hands thrust into his trouser pockets, eyes forward and with purpose. It wasn't as though he had set out with the goal in his mind to meet people from his past. In fact, he was generally staying at a slight distance from those of his community, simply out of habit. He was used to living among muggles. He visited his home and community on his time and his terms. The notion that his two worlds, in a way, were now combined didn't sit well with him and he was still trying to find a balance. Yet, seeing the open invitation to everyone from his world placed by his Grandmother that so blatantly excluded a man from his family's past caught his attention. He wasn't going to scold a woman he didn't know. He'd not tell Lily or any of the Marauder's how to respond to Peter. That was their prerogative. But, with that in mind, he also didn't expect to be told how to respond to the man. No one had questioned him, yet, and he was glad for that.
He felt the need to find out a few things about Peter, especially bearing in mind the year he originated from. 1979 was a gray area, where it could go either way in saying whether Peter had yet to betray his Grandparents or not. And Albus wasn't going to pretend to be able to tell. He hadn't known the man. But, statistically, Albus had doubts on the matter and if the man hadn't yet betrayed his fore bearers, he did find it to be awfully cruel to segregate him from his entire community. And Albus was aware that he was likely one of the few who felt this way.
He didn't really care.
Stepping into the mess hall, he walked right up to Peter, pulling a hand out of his pockets to extend in the man's direction. "Hello, Peter," he said in a pleasant enough tone.