[SpaceNugget]

If someone speeds up when they see a car in another lane signalling that they are going to merge, in order to prevent that car from safely merging, when the merge would have been safe to perform had they not sped up to prevent it, they are definitely driving incorrectly.

[practicemaths]

If a car does that then it's not safe to merge until after they've gotten ahead of you.

[myko]

Exactly, which is what I said in my earlier comment that you seem to have misunderstood.