The conflict lines shown in the article are not present in the file, they are a display of what has already been merged. The merge had changes that were too near each other and so the algorithm determined that someone needs to review it, and the conflict lines are the result of displaying the relevant history due to that determination.

In the example in the article, the inserted line from the right change is floating because the function it was in from the left has been deleted. That's the state of the file, it has the line that has been inserted and it does not have the lines that were deleted, it contains both conflicting changes.

So in that example you indeed must resolve it if you want your program to compile, because the changes together produce something that does not function. But there is no state about the conflict being stored in the file.

In this model, conflicts do not exist, so there are no conflict markers (the UI may show markers, but they get generated from what they call “the weave”)

Because of that, I think it is worse than “but it is not valid syntax”; it’s “but it may not be valid syntax”. A merge may create a result that compiles but that neither of the parties involved intended to write.

Yeah this seems silly. You can do the same thing in git (add and commit with the conflict still there)! Why you would want to is a real mystery.