What is the main use-case for this? I'm looking at it from a coder's perspective. When I'm writing some code I wouldn't want somebody else inserting characters into my code while I am editing it.

But I can see that if the app is divided into a multiple code-files then different coders can be working on different files at the same time. Still I prefer some form of code ownership or at least locking of multiple files just for me while I'm working on them.

I don't quite see how it would be much different for other kinds of text. While I'm writing this post right now I wouldn't want somebody else modifying its beginning while I'm writing its end.

Not saying there aren't any good use-cases, just can't think of any right now. So that's my question, what are they?