Two weeks ago or so I had a conversation with your support. I had a problem with a project I transfered to a client.
The client started editing the content of the page and was getting lots of weird/unexpected behaviour, like multiple elements changing, css messing up. Stuff that really confused the editor and modified the page in an unwanted, unintended way, tedious to repair.
Turned out the outdated browser he was using (Safari 6) seemed to be the problem. As you write in the webflow system requirements, old browsers can lead to unexpected behaviour.
I found this page after running into the problem and using my, the client's and your support's time to resolve the issue.
Now, thinking about it makes me wonder: Why allow editor access with incompatible browsers at all? If there's a chance of really damaging the project, why not block the troublemakers and throw an "upgrade your browser message" instead?
Nobody would ever edit, if things can go that wrong.
Could really save some time and headaches in the future.
PS: I like that webflow uses latest browser technology.