Just above water line thru hulls

H 22.7f:

f. The discharge location shall be above the waterline created by maximum conditions of the boat's loading, heel, trim and motion astern. EXCEPTION: The discharge may be located below the waterline if the discharge line is provided with a vented loop to prevent siphoning into the boat. A check valve shall not be used for this purpose

Re-read the definition of "waterline" in the rule above. That's the waterline that counts.

Why would anti-siphon on an A/C line not be an issue? Because it flows back to the intake?

So given all the hoses, piping and connections associated with an AC system, it wouldn't make sense NOT to have an anti-siphon loops(s).. now would it?

As for sumps, again, the little valves are there to prevent backwash of water remaining in the discharge hose into the sump when the pump turns off, not as a replacement for an anti siphon loop. Check out the instruction manuals.

Caltexflanc here is the correct standard, requires some more digging to get to the actual meat,
http://www.tc.gc.ca/eng/marinesafety/tp-tp11717-menu-808.htm

The a/c pump a lot of times doesn't produce enough pressure to open them. Or if it does they restrict flow, so you usually avoid them on an a/c pump.