Ok, see if you guys understand me this time.

Basically, I know how to spot an enemy Decoy Commander. How?

Well, hover over the Commander in question, hold shift. What's different? The decloak radius of a Decoy is very small in comparison the Commander, so you can easily spot a fake.

Secondly, the radar coverage of a Commander is shown as blue when holding shift over it (sonar?), now, a Decoy has a green ring instead. I'm guessing this means the Decoy has no Sonar, which, if true, please add.

Now, Morph's an easy one, hover over the Commander and hold shift, has it got a big radar? Yes? Bingo.

I think this might be a Spring Issue, but I dunno, in any case, could do with being fixed.

I'm probably one of only ones who knows about it (noruas didn't really understand me and I had to explain it to Jools, Ansik, BD and Jim a bit) but I've battled for Decoys to actually act like Decoys, might as well finish the job.

imo you should see when a com is morphed, this should not be a secret. whereas of course you shouldnt know whether its a decoy or not :/
another way to find out whether somebody is morphed is to use the tooltip widget and when you hover with the mouse over the com in question hold spacebar. (i think its the tooltip widget that makes it possible but im not sure)

i give a +1 for fixing that with a gadget

OR, just use the commander name tags widget :)

Ban widgets...

Is the decoyFor unitDef tag being used properly?

I took a peek in the unit's fbi file and it seems to be absent

so it will be fixed in the next version?

It shall be fixed then.

You do realise you can just watch him walk fire or build, and immediately tell it is morhhed?

Decoy com thing I reported ~3 years ago.