You're saying if I sell 1BTC on Bisq and I suddenly get $20,000 via bank transfer, which on other days doesn't happen too often, the bank is going to ask questions?
Yep. It may vary per country, but I'd expect a letter asking many questions (just shy of the color of my underware).
I mean, you could just reply to those questions honestly and say you bought BTC at a certain earlier point in time and sold it online. I don't think it would be a big issue
They'll also ask to know a copy of your taxes, including your savings at other banks. Privacy? Lol. If you don't like it, they'll close your account.
it's going to be similar to buying (or selling) another expensive item like a car.
Not really: the car is traceable in your name.
If you're in a country that has property tax (I believe such as LoyceV), and plan to sell it for fiat in the future, make sure to tell them yearly how much BTC you own (denominated in fiat) and you can hold it anonymously (no need to hand public keys or anything like that) without problems.
I think the proper term in English is a wealth tax, but indeed, filing it and paying your annual taxes avoids jail time if you ever buy a jet or something.
Then, when the day comes that you're selling it all on Bisq, there shouldn't be any issues. Since they can go back and see that you always declared ownership of them and paid your taxes on them.
You'll be fine, as long as you answer all privacy invading questions your bank asks.
In general I don't think using a centralized exchange to do something illegal in your country, is going to make it legal. If you follow your laws in the first place, you can pretty surely sell P2P without worries.
From what I've seen, using an established exchange makes the bank "easier" because they know at least the other party isn't a criminal. Now let's say you sell 1 BTC and receive $20,000
tainted dollars P2P. Then what?