Quirk 1: You can run into certain corners/nooks to slowly gain height (which you can then jump from)

Quirk 2: You can input multiple jumps upwards into a hill to get extra height (tip: right click and space bar are both bound to jump).

These are just my descriptions of them as I've experienced them and may not be totally accurate. From what I can tell Quirk 2 is easier on steeper hills, in addition there is various terrain that you can run directly into that will occasionally push you backwards which then makes using Quirk 2 easier.

Made two videos showcasing the quirks: one using a mouse macro (to show what's theoretically possible) and one without.

Here's a very trivial spot to try it out, simply mash jump (most fences that look like this seem to be fairly easy to climb).