signature is converted is some cases

Hi,

If I write a new email, the signature is not converted. However, if I answer an email, my signature is converted. I noticed that when I write a new email, the signature is preceded by the '--'. But when I answer the email, the signature is not preceded by the '--'.

My signature settings are :

"Automatically quote original message when replying" => checked When quoting "start my reply above the quote" and place my signature "below my reply (above the quote)"

I tried adding '--' to the signature or typing it when replying but signature is still converted