If I’m on a bike, notice a car coming up behind me, and don’t think it’s safe for them to pass, I will put myself in the middle of the road to block them.

If they try some stupid and dangerous passing, I’m the one getting pulped. Putting yourself in the middle of the road is a very effective way of communicating “don’t even try to squeeze past me, there’s not enough space.” The most dangerous situations I’ve been in on a bike have been due to cars trying to squeeze past me when there isn’t enough space, it’s terrifying.