I'm with you on this - but a similar thread on the Flyer portal saw me derided for suggesting that the weedier end of the aircraft spectrum could be modified as such.
My POV came as a motorbike rider (and a newbie PPL-er) having seen adjustable baffling systems on race exhausts. Could the engine not be allowed to breathe free and noisy for take-off where the power is needed and baffled/stifled for cruise and approaches?
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If it ain't broke - why not?