Signature in Service Tickets depending on the category

Hello everyone,

one customer of us requested this feature. The signature should be added automatically to the answer after clicking on "Answer" or "Answer to all" in the ticket. He has templates for each ticket category and want this to be taken depending on it.

We didn't find an event for opening a new reply in crmscript. The current idea is to replace the default user signature every time the ticket is opened:

Is there a better way to do it? is that even possible?

Thank you in advance!
Best regards, Andrey