If you sent someone a text message that said
By melinchina on Mar 21, 2007
"Sorry, I'm going to be a few minutes late for our appointment" and the person responded "ack", would you assume:
A) They're surprised and disappointed (a la Bloom County)
B) They're sending you a snippet of networking code that means "acknowledged"
A), right? Totally. Me too. I sent back a message saying, "I'm so sorry! We can re-schedule".
Turns out it was actually B in this case.