I think it comes down to personal preference and hand comfort. I have my bar end cables untaped and there are times when it bugs me. When I'm shifting at speed I like to grab the end of the bar and shift with the rest of my hand--with the cable untaped I either have to grab it in my hand too or slide my hand under it. OTOH, I've wondered if leaving them untaped is wise from an ease of maintenance point of view--don't have to undo the tape to replace the cables.
I'd recommend taking it for a short ride without your bars taped and seeing if anything about having the cable untaped bothers you.