I edit videos as part of my work. I have a master's degree in this very subject, so it's safe to say that I've done a lot of editing. A lot.
I know customer support, GMs and such have said in the past that they cannot accept video evidence because it could be edited/tampered with. But I'm not sure they really know what goes into actually doing that.
It's not as easy as, say, photoshopping an image. You can't just "erase" characters out of the scene or edit the clip to make it look like they're doing something that they aren't. Just like with real-life movie composition, you'd have to meticulously set up a scene, get the right angles, take multiple shots, sift through the footage, etc.
It's a lot of work.
And I mean, really - who is going to go to all that trouble in a video game? Even if they did - it's really easy to tell. It's not like editing an actual, real-life shot because nothing is scripted. Every player character is moving independently of each other. Even the best video editor can't simply splice things together and make it look smooth and seamless.
And even if someone takes a clip on Twitch, it's saved on the server. Here again, even if someone downloaded it, edited it and reuploaded it, it would be easy to tell at a glance that it was tampered with. Now, I'll grant you that video evidence alone shouldn't be the only determining factor in whether or not action is taken against a player.
But legitimate PVPers -- who play by the rules -- are tired of being curb-stomped by people who manipulate the rankings and playing field for their own personal gains. We know GMs have access to combat logs, so they can see how much activity was done (or not) in a given timeframe, but that's an awful lot of sifting to go through, when video evidence could lend more credibility in addition to existing text reports.
I just wanted to voice my concern and maybe help shed some light on what is really involved in editing such things.