So, while I was making my map, I found out that the nametag of another player was shown, even though they were invisible (this is not the case in 1.7). It looked like there was a nametag floating in mid air. The player was in a team, but no further modification has been done to the team except for changing the color. I'm pretty sure this is a bug.
Duplicate of MC-48730 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.