what are you doing when a password from a weak site gets compromised exposing your algo?
How do you memorize your "unique" key?
For example on HN my password could be 1YCju7i8!
It isn't, but let's pretend it is.
That is a counter at the front, YC is from the website address, j from my user name, and u7i8! It's the unique key. I use the same key everywhere so it's easy to remember.
I don't think a hacker would figure it out.
I think you have a valid point in multi site leaks if the attacker was focused on my account. I will think about it