I wouldn't clip a real Walkman to my belt, let alone the majesty of Soundwave. Far too much risk of either falling off. But as for knowing Soundwave does this, I think the presence of a belt clip is a bit of a giveaway that he can be clipped onto belts.
It *was* a secret! No one at school who had a Soundwave attached it to their belts! This feature has never been mentioned in any online or offline chat I have ever had about the toy with fellow fans! No guidebook has ever mentioned this!!!
Er, yes, and I never considered it a secret, just something too obvious to need mentioning. It has a belt clip right there on it's battery case door. Yes, wearing a dictaphone on ones belt is an odd thing to do, but Yuppies used to carry filo-faxes under their arms so it isn't even close to the silliest thing that real humans have done.
This is a strange question - it is like asking if anyone has ever aimed through Megatron's scope, or put his stock against their shoulder. What is odd about using a feature that is present on a toy to do what that feature is designed for?
(Remember, the cartoon and comic both depicted Megatron's alt-mode as several times too large (I'd eyeball about four or five times the size it should be - the toy is actual size in dictaphone mode rather than the massive blocky thing that was usually depicted in the fiction. In the same way as Skids was depicted much larger in vehicle mode than he should be.)
I just checked the back of TR Soundwave and the moulding there homages the back of the original Cassette Man and this nonsense 'belt clip' is clearly seen there but of course the toy would not homage a feature THAT NEVER EXISTED!!!