I don't think this really applies here. The commenter isn't saying "why would anyone use Dropbox when they could just roll their own with these open source tools", they're saying "this product is a good option for those who are specifically looking for an open source alternative".

He's referencing a comment from the original Dropbox announcement thread (linked). It's famous because it misses the point of Dropbox spectacularly.

Sure, but Syncthing doesn't miss the point at all,so it's slightly out of place to bring up that line.

Or does it? You certainly wouldn't run into an arbitrarily imposed device limit.

It’s interesting to see how FTP became so fringe, when at a its peak pointing a browser at a FTP url would be enough to browse anonymously.

Right, but my point is that the person he sent it in reply to didn’t miss the point in the same way.

I thought it was frowned upon to use version control on binary files? Or is it just git that doesn't support them?