I’d add arguing by using inline quotes. Example:

some snippet of text from parent comment

I disagree because x, y, z.

another snippet

This is wrong because a, b, c.

(End example)

Doing so obliterates context from a position, especially long form comments (which is the main reason I’m here) in two main ways. First, the technique rarely reproduces the parent in its entirety, picking out black and white statements that are easier to argue against from a sea of nuance. Second, it cuts up the narrative in such a way that downplays the rationale of a position by either leaving out reasoning, or placing arguments between the reasoning and the conclusion.

Sure, the readers can go back and reread the parent. But when the structure of an argument depends on those snippets (and it almost always does) it becomes very difficult to grok.

Generally I just see it as a big warning sign that the quoter is more interested in winning than learning or getting to the truth of the matter and thus is best ignored.