OK, yesterday I borrowed a memory scope to look at the serial signals from the A210. I connected the scope to the RX line of the A210 (SV pin 6 TX) and observed that whenever I pressed the TUNE COM button a little serial blurp appeared on the lines the signal went from idle at -4.3 Volt to +8.3 Volt active and the whole message lasted for about 31 ms, so a completely valid serial rs-232 interface. Then I monitored the returning signals: TX line of the A210 (SV pin 5 RX), I observed an idle signal of -6.5 Volt but the A210 didn't send anything. So the A210 output just sits at an idle rs-232 level and no key presses on the A210 result in any outgoing messages.
So the final conclusion, the SkyView to A210 interface allows for setting the backup frequency (but TUNE COM needs to be pressed twice), but the the ICOM A210 version 1.53 does not in it's standard configuration send out any information regarding the selected frequencies, so SkyView can't display anything (resulting in a big red X).
This mean that unless a configuration is found that makes the ICOM 210 send out data it won't work with the SkyView COM status display, and in the nominal configuration menu there are no options related to the ICOM serial output interface. Also since the TUNE COM button only appears on the SkyView when the COM status input is enabled the TONE COM is only available for users that are willing to live with a big red X on the SkyView top line