I am another one who is catching up.
1. Not much comments here – at least I feel like I understood them after reading the discussion here.
2. As a non-native speaker of English, I am not really convinced about the modality principle. I have always been more comfortable with seeing text in general. Of course, this depends on various factors in real life.
At last, I personally do not see much difference in use of text in PowerPoint slides between students and academics, and it seems to be up to individual.