Signature not shown for some users & login problem

Hi,
1) for some users, the signature is not shown in their posts, although the users defined it in the signature field.
For my profile, I can confirm that the signature is shown, so it is not just a settings problem.

Additionally, I have a user who always sees dots in the password field, when he wants to log in. He then deletes the dots, tries to log in and gets the message "password not correct".

He reloads the page, again the dots, he deletes the dots, then it works. He tells me this happens every second time.

The user with the login issue also has the issue with the signature (more details about the users in the hidden field)

Thanks!!!