I succeeded in having the RM-VL710 learn all the AC remote commands I wanted.

I'm not sure anymore that there's an infrared feed-back, I think the problem was that I always tried to keep the AC remote buttons depressed until sony acknowledgement like the manual suggested; even when I tried to keep them pressed for a short time as I said in the original post I evidently still unconsciously kept them depressed longer then necessary to 'help' the sony remote learn.

Now I just programmed the sony by clicking on the buttons very quickly, like in normal usage, and then waiting 1 or 2 seconds, w/o doing anything, for the sony to acknowledge them.

Now I'm very satisfied. Certainly the sony lacks the AC remote LCD status, but during normal usage that is almost useless, however there are things that I can do now with a single key press that previously would require 'cycling': there are some keys on the AC remote which work though cycling (ie there's just one key for "fan speed" and you press it many times to get speed1, speed2, ..) but apparently this doesn't not work like for instance sony TV AV1/AV2 where it's the TV which cycles through AV in response to the same IR command; the AC remote actually remembers what it thinks it's the
status of the AC and sends different speed IR commands (even if you use the same remote button) depending on the last used, so I could program on the sony the 5 fan speeds on 5 different keys, and now I can go to the desired fan speed directly, w/o cycling.