During the final moments of some of the faster speedruns, I've notice people climbing walls with far reach. Ex. Cearadeth.

How do they do this?

F-Cancelling. When you're in the air and using far reach, press F to cancel the far reach before you reach the spot you "blinked" to. This will allow you to do far reach again while in mid-air, which allows for some sick heights. This only works on version 1.3 or earlier, and the latest patch is 1.7, so make sure you downpatch before trying it.