In T153255 and T166868, the idea of making it easier for new users to figure out how to sign their posts was raised. A few ideas were discussed that weren't tenable, but there was an idea that is relatively lightweight and might help somewhat:

In T166868#3310438, @TheDJ wrote:

Simpler idea.. When first time visiting a talk page in the editor, popup a 'guided tour'-like dialog. "Did you know that you can sign your post on a talk page by typing ~~~~ in the editor?" etc..