I've lost count of all the sites where I sign up and paste a long, secure password generated by my password manager. One of three things happens then.
1) The site admins are competent and my strong password is accepted.
2) The site admins are incompetent, and limit password length to a short string, possibly with certain special characters required.
3) The site admins are incompetent and should immediately be fired, because the form accepts my long, strong password, silently truncates it to a shorter length and saves that, and my correctly typed password no longer works. I've discovered this pattern repeatedly after comparing the 'forgot password' email then send with the truncated password in clear text (which is another reason they should be fired immediately) and noticing it is much shorter.
First-world problems, I know, but this annoys me and I would like to see it fixed.