Accents, I can deal with.
But try having a *blind* teacher. Yes, blind. He'd feel around for the blackboard, draw horrible zig zags he called diagrams, bump into things, it was almost sad to watch. But he was a damn good lecturer. Loved the class.
And then, I had a teacher with Parkinson's. Also sad, but he'd shake and convulse and turn uncontrollably, while trying to explain discrete transforms, decorrelations and wavelets functions for image/video compression.
One of my profs was also 80 years +. Who knows why the University kept him, but he was intense. Could fill the entire blackboard with formulae in a matter of minutes. He'd stare at the floor when he taught, never looked at us. Would smack his chalk on the board, send shards flying.
My best prof was for Algebra, though. He'd show up wearing a terribly old and dirty t-shirt with some faded hockey team logo, some silk PJ pants, uncombed hair and hiking boots. Like he just got out of bed 10 min earlier and wrestled a bear on his way to class - he'd just walk in, and start talking about Eigenvectors and change of basis matrices.. just keep going and going, past the hour. We'd walk out to our next class, he'd still be there, writing on the board.