Other than 3 dogs on yo-yo leashes walking their one "master", my only greenway pet peeve is two trikes stopping in opposite directions across the path width to chat about their trikes.
Different parts of the trails vary in pedestrian traffic. It tends to be that around park trailheads there will be a lot more pedestrian traffic, which should be anticipated.
I pick my gearing so I will not exceed 20 mph, but am normally riding 15.

It's a normal reaction when you're rounding a blind drop on a greenway/MUP to react negatively to people standing their bikes in the path.
When you see it's because of a wreck, that reaction goes away. That doesn't mean you haven't already voiced an objection.