Individual name tags are not possible right now... In first place, they're rendered with the player entity, and in second place, name TAGS are not implemented in MCPE yet xD If you see something like that... It's because the server has hidden fake players within blocks xD
This is impossile but I think it is possible to replace the player name in the message at the time of sending the message to make it appear above the player
Actually... This is a glitch on a sign that is really cool. How To Do It: place a sign go to last line hit 'shift' then hit return/enter repeat 5 times Type and done!
use specter and/or essentialspe which brings the /nick command. Now, Type /s new <name> Type /nick <nick> <setname> And one way you can do this (for multi-line message) hold shift & press enter.
Yeah, long nametags and greater formatting are now possible, with the old api 16 chars were max and only small symbols were supported as a modification