An item that has both the glowing effect and a visible custom name has a very blurry nametag. This does not apply to mobs.
Test Command:
/summon Item ~ ~ ~ {CustomName:"Mr. Test",CustomNameVisible:1,Item:{id:diamond_sword,Count:1},Glowing:1}
A picture is attached to demonstrate the issue.
Environment
Windows 10 build 10240, Java version 1.8.0_25, NVIDIA GT 745M
Confirmed.