No and Yes. "We will receive SEPA transfers in EUR and will convert them to USD according to our bank exchange rates."
Bitstamp trades pair BTC/USD. Not pair BTC/EUR.
You can swith to BTC/EUR.

of course, that is simple math. But the trades are i USD. BTW, we have in Europe not only euro. Euro is miserable currency.
as far as I know you can trade $ AND . the market is not really deep and it is hard to get larger orders through. it is separate from the $ marketplace
Yes, you are right.
You will send them the euros, and they will convert them to dollars. It is not trading in euro.
No. Stop spreading disinformation. If you have your account in euros everything goes in euros, deposit, withdrawals, trading...
Look:
Important notice
Your SEPA deposit will be credited in 1 - 3 business days. All funds transferred via this form, will be credited to the selected account balance. If you selected USD balance, your funds will be converted respectively. Check our current exchange rates here.
As my account is in EUR, it is USD what will be converted to EUR, not viceversa.