When adding a Conditional field into a signature template you're unable to add a vertical line( | ) inside of the conditional.  If you're still needing to add a vertical line in you can add in a variation that will work. 

Here's the line:  │  

The html would be: │

Here's an example what it would look like in the signature template and the preview:

{|FirstName|} {|LastName|}[|│|JobTitle||]

David Aulick│ Test Title Run 5