What if we could notify the user as soon as another editor changes the same page as you are editing? This would give a signal that edit conflicts are likely, and the current edit should be minimized and saved as soon as possible, hopefully making a conflict less likely, or easier to deal with.
This has been discussed before, see T137318#2438653 and related pages. As far as I can see and remember, the conclusion was that this needs more research on whether this actually helps users or on the contrary scares them away, and that in a quick prototype 80 % of all users didn't notice the info shown that another user edited the page.
@Reedy @Schnark Thank you for the thoughtful links, and apologies for the ticket spam. So many things are annoying about edit conflicts... I spun this task out while working on another aspect of the problem, and hadn't put any time into background reading about what has already been tried.
It's probably best if I just close this for now, since it prescribes an overly specific solution that isn't backed by any consensus.