The user can still create a signature, it just isnt displayed on viewtopic, profile and when reading the users PM.
Viewtopic:
Open styles/prosilver/template/viewtopic_body.html
Find:
<!-- IF postrow.SIGNATURE -->Replace with:
<!-- IF postrow.SIGNATURE and postrow.POSTER_POSTS > 15 -->Profile:
Open styles/prosilver/template/memberlist_view.html
Find:
<!-- IF SIGNATURE -->Replace with:
<!-- IF SIGNATURE and POSTS > 15 -->Private messages:
Open styles/prosilver/template/ucp_pm_viewmessage.html
Find:
<!-- IF SIGNATURE -->Replace with:
<!-- IF SIGNATURE and AUTHOR_POSTS > 15 -->Save, upload and refresh the template.