I have the issue in two different database's that helpdesk and SO emails (written in the send message chatter pr autogenerated) are send from the email of the creator of the ticket, and signed with the signature of the creator of the ticket rather than from the user who is writing the message. It seems like the template uses the following information: 

${object.team_id.name or 'Helpdesk'} Team. and
% if object.invoice_user_id.signature:
${object.invoice_user_id.signature | safe} % endif 

However this leads to the creator being filled in rather than the user of the document. Is this a bug, is this standard behavior or can this be changed?