The signature panel displays even when a user does not have the auths to create/edit their signature.
modules table lacks acl_u_sig for signature module
In light of https://github.com/phpbb/phpbb3/pull/712 and http://tracker.phpbb.com/browse/PHPBB3-10664 I believe the fix here was incorrect.
The modules table entry for signature module has no acl requirement. Whereas the requirement should be u_sig. Instead of performing the check manually in the code as had been done in the merged patch, the modules table entry should be altered to include correct acl requirement.
Signature reference was actually in the topic here: https://www.phpbb.com/community/viewtopic.php?p=13114326&sid=a28f64d7f083d70bbcebc112d17e21ac#p13114326