Ok, If you load a fresh world on this snapshot and place a soulsand block. Stand on it and the light levels are normal. Place a dirt block on top of the soulsand, then destroy it. If you stand on it now, the light level is 0.
I believe this is fixed in 14w30b.
Close this bug report please. I can't use search tonight. Duplicate of MC-35860. It may work as intended, but it sure is annoying.
confirmed for 14w27b
Confirmed for 14w26b
This affects 14w25b also.
When looking at your character in 3rd person, your feet go inside the soulsand when standing on it.
Confirmed for 14w20b
Confirmed for 14w19a
confirmed for 14w11b also
Video of issue as of 14w30b