[jamwt]

Sorry, not super familiar with Syncthing. It's definitely not impossible to do better than Dropbox, but to some degree, as in all things, it's a function of engineering resources, telemetry, and usage.

We've likely put 25-100x more resources into solving this problem over the last 10 years, and we just have a lot more data b/c we have 100s of millions of users on lots of platforms using Dropbox with every application you can imagine. So we're able to tease out the "long tail" of weird file system and application behavior in a way that's very difficult for smaller projects. Truly durable conflict management in the face of arbitrary mutations by user applications on the filesystem ends up being a really, really hard problem to cover exhaustively. The Dropbox client handles literally hundreds of special cases.

So, yeah, I believe it is (in general) safe to assume that Dropbox is probably doing A-more-correct-thing for a complicated (and admittedly confusing) reason when it comes to sync behavior. But we're not perfect--we do still find surprises from time to time, so feel free to contact support if you see something that looks wrong!