In the source mode: Type your comment, see your signature in the live preview.
In the visual mode: Type your comment, wonder whether your signature will be automatically added. If you type ~~~~, then you will get a long message that says your signature will be added, but if you don't type that code first and read the message, then you don't know what will happen.
From User:Schoffer at https://fr.wikipedia.org/w/index.php?title=Wikip%C3%A9dia:Le_Bistro/24_novembre_2021#Rappel_sur_le_test_A%2FB