Uhm, atcually, the client that i was using is unmodded. This was a Custom-built map by Vechs, and he Edited the spawner's NBT tag.
I was also i single Player.
Also notice how name tags in MP and any particles also have the same effect.
It has the same effect on any thrown projectiles, too. (Thrown Ender Pearl, Thrown Snowball, etc.)
Daniel 
MC-4038
MCPE-1953
Do you want me to delete this post, then?
Same here.
Uhm, atcually, the client that i was using is unmodded. This was a Custom-built map by Vechs, and he Edited the spawner's NBT tag.
I was also i single Player.
can some one else prove this? here is a link to download the map that i was playing on : http://adf.ly/1603544/giftwarped
That mod is Optifine!
I believe that this has the same effect as destroying a bed.
Notice how they both "light up."
I didn't know that java was already at version 7! Last time I updated, i checked the version and it still said version 6 update 12... i think.
I have seen this bug.
Also notice how name tags in MP and any particles also have the same effect.
It has the same effect on any thrown projectiles, too. (Thrown Ender Pearl, Thrown Snowball, etc.)
@Ezekiel I agree, and also if it will help, the IP to the server I was playing on when I took the screen shot is play.itsjerryandharry.com
Its a bukkit server, but its the name tags are client-side.
Confirmed