Sorry I can’t help very much because I don’t have M4L. I only have a freebie copy of Live Lite I got bundled with an interface I bought a few years ago. Even though I cannot run M4L devices I’m a curious sort, so I loaded up Iannix’s Live-set with my copy of Live Lite 8 and this is what my channels look like:
I see that “Iannix_out” is instantiated as the MIDI-In for both channels, so if you have M4L, I would expect it to be receiving MIDI messages from Iannix running “Simple MIDI example.nxscript“. I know for sure that score generates MIDI messages. However, unlike the example screen shots provided by Iannix, I found no way to get those ports to appear in the MIDI Preferences. I do not know why — maybe that’s a function of M4L. Hopefully one of the Live-8/M4L users will see this thread and help.
No, MIDI Yoke should not interfere, and if I were you and I had no luck instantiating ports via those Live channels, I would experiment using Yoke as the buss. But first I’d try to get one of the M4L users here to help out because none of them mentioned using a MIDI inter-process buss like MIDI Yoke or NTONYX, so I’m guessing Ableton Live can instantiate MIDI ports via its own virtual devices.