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or I am mising something ?
Yes (language) , that would the reason why its called echo all, not echo!
Thus theres nothing there that says maya would stop echoing, it just does not echo debug and secondary effects. The definition of on and off is not this or opposite this, grantted if you turn of your display it shows nothing but that does not mean its doing nothing but if you have switch labeled lift up on/off does not guarantee something moves down because you move it to lift up off just that it stops moving up (it might, a real lift wouldnt but a specially wrongly constructed could, a lift where the up engine is off does not go down. And to hollywood fx guys a lift with severed wires goes nowhere at all it stays put! It does not actually depend on the wires alone, rather the wires suped a set of wedges that go off in case of wires braking load limit overload or too fast speed down). Here it means exactly that it stops echoing everything, in way the on off only apples to the all part of the text (writing all wouldn't be same now would it).
You cant really stop maya form echoing stuff because the mel maya echoes is what maya does. Echo all is there just to suppress the bulk of stuff that would slow down maya execution to small enough data steam to make it effectively buffered. Besides theres no reason you'd want to either because that would mean there wouldn't be anything in the history window ever.
If you need to record your own stuff make a new text window and inject it there
PS: this must be the frst truly new question on this board ive seen in long time.