I'm usually such a stickler for proper spelling and punctuation that I could be a crochety old grammar teacher. That being said, seeing Sam's Valentine card addressed to "Mome" warmed the cockles of my hart. (What are cockles anyway? I guess it really doesn't matter what they are. The important thing to focus on is that they were warmed.)
It's called "sound spelling" which is new since I went around that block back in the last millennium. (Scary thought, huh? Let's not dwell on that for sanity's sake.) It's actually a great idea because kids spell a word by literally sounding it out, so there's no real "right" or "wrong" answer. The focus is on phonics, not rote memorization. That is until spelling tests begin in a couple of years, of course.
The spellings are hilarious. Deep down, though, most of them really do make sense, sometimes even more sense than the correct spelling does. So here's a random sampling of Sound Spelling by Sam for you -
ax = axe
rivr = river
foling = falling
speshl = special
bcos = because
trtl = turtle
Sindy = Cindy
There is one word he has down flat, memorized and imprinted directly on his brain from reading it over and over all over his toys, books, boxes, magazines, and pamphlets -- Lego! I'm not sure how understanding he would be if you sound-spelled that one wrong!