// Knight lost half a billion dollars in 30 seconds. Nobody reversed though, even though it was clear error.
You cited Knight twice in this thread, and it's just not the same concept. I think your point is that people should accept irreversible transactions in whole because there are some edge cases where they exist today, and that just doesn't make sense.
First, there's a difference between an average person and Knight in the degree of sophistication of tools that they can wield. So the fact that Knight is allowed to operate like this is in no way connected to whether this mode should be the default for an average person.
Second, the Knight example can be interpreted as an exception that proves the rule. They had an unforced error that (from what I recall) looked to the rest of the world like real trading. But there's a whole other slew of issues (clearly bad prices, exchange-errors, etc) that cause trades to be unwound. Some exciting reading if you care: https://www.investopedia.com/terms/e/erroneous-trade.asp
You have a point that yes to some extent we're all subject to underlying risk of irreversible activity but the bigger point is that we as society try to minimize it where possible. So moving the system in the other direction, especially where it makes it easy for Joe-Blow to fuck it up, is not the way.