These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Growing the Beard: Arcturus Rann, literally, when he sacrifices part of the his artificially-maintained youth to recreate Biotron.
They Wasted a Perfectly Good Character: Huntarr wasn't under any licensing restrictions barring him from usage as he was created by Bill Mantlo for Marvel Comics. Given his extensive character development and excellent relationship with the other Micronauts, the fact that he didn't return with Rann, Mari and Bug is puzzling.
The entire notion of the Microverse has been laying fallow for many years in Marvel: even if they have to write around trademarks, you'd think they'd take more advantage of this science-fiction setting existing literally just under the noses of their regular universe. Reed Richards is known to have the technology to shrink objects past the barrier: it's a surprise that he didn't employ it in Civil War as an alternative to the Negative Zone.
When Genis Vell and Rick Jones were sharing a body, they would swap places between Earth and the Microverse. Rick had had a similar arrangement with Mar Vell years earlier, except they swapped between Earth and the Negative Zone.