This is years ago now, but every ampersand in my passwords came across wrong. I can't recall if it was missing or url encoded, but even passwords weren't safe.
I want to as well, but annoyingly there are many sites that insist on a "special" character because their strength measure says "low" for the 20 character alphanumeric string I generated %-}
My favorite is when they actually limit what special characters you can use. Must include 1 of x special characters. Why? I always just assume they baked their own password storage and couldn't figure out how to handle the whole set of special characters
Multiple times I've found that this is caused by a web application firewall that is intended to mitigate SQL injection attacks. So they disallow the characters that would commonly be used in those attacks.
On those sites, I generally insert the same fixed uppercase-and-symbol string on my zbase32ed-entropy passwords. Zbase32 tends to produce numbers already, and that combo tends to satisfy the silly sites.