Don't start a reply with "this is totally incorrect", when you're merely pointing out a simplification or approximation. I was making a point about the busines

Don't start a reply with "this is totally incorrect", when you're merely pointing out a simplification or approximation. I was making a point about the business model of a proptrader marketmaker versus the business model of an algorithmically sophisticated broker and needed to establish some preliminaries and it would have served zero purpose to go into the particulars of the costs related to risk warehousing. Having worked for an equities highfrequency marketmaking business myself: Mark-to-market at mid-price is the benchmark that those traders will use for figuring out, at the end of the day/week/month, whether it was a good or a bad day/week/month, and at the end of the year for negotiating their bonuses, even when they are left holding some positions with uncertain future. Everybody knows that it's a simplification/approximation, but, due to the efficient markets hypothesis, it's a very good one. It's the kind of approximation where it's being taken for granted that people understand that it's not ACTUALLY the trader's profit. Because otherwise one would need to include in the discussion the fact that the receptionist at the proptrader marketmaker's office building is also a cost factor eating into their margins. I didn't mention the risk warehousing for the same reason I didn't mention the receptionist. And I'm not going to go into a rebuttal about how it's definitely not necessary to hedge every single trade, for the same reason: because it's not the topic under discussion here. It's called the "maxim of quantity" and it is a generally-accepted maxim of conversation. (see https://en.wikipedia.org/wiki/Cooperative_principle https://en.wikipedia.org/wiki/Cooperative_principle) Maxim of quantity: * Make your contribution as informative as is required (for the current purposes of the exchange). * Do not make your contribution more informative than is required. So, to conclude: Your conversational move in this language game was a pretty weak one. The sentence "this is totally incorrect" however sounds like someone trying to establish dominance. Weakness and trying to establish dominance is a bad combo.