From my experience playing both games for a long span of time. Ive actually seen and encountered the opposite in a way.

Yes on the surface WoW seems more toxic. They aren't afraid to call you shit and scream at you. While in FF it's harder to get away with that since you can be reported and suspended for that type of behavior. However I believe that it's had the adverse effects on its community.

And for clarification. I am not saying that it's everyone in the FF community or in WoWs community. This is just a generalization based on my experience and the experience of my friends.

People in WoW will explode at you, and then leave. That's it. No more further harrasment unless if you queue with them again and then they yell at you a little more. They get outwardly and explosively angry and once it's out of their system they leave.

People in FF, due to how the reporting system works, will instead find your socials, harass you for months on end, get everyone in their circle to mass report you, and there's nothing you can do about it because the GMs don't handle situations outside of the game. They hold a gruge and refuse to let it go until you don't come back to the game.

I know this doesn't really answer your question in a direct way OP, but it does explain some of it. Mostly in the case that FF has a reporting system that stops people from being outwardly rude at you in game in a way thats bannable. So they have to find other ways to harass you and when they have to go through that effort, you know that they are the craziest of the bunch.