I do this ALL the time with everything/anything that needs it.
I slice up my tracks into "chunks" when possible...and things like vocals or leads make it very possible, though I'll slice up a drum track if need be, even if it's just a single snare hit...and then raise/lower the level for that one object.
In Samplitude...this is not a destructive action, so the original waves are never changed.
Also...this has nothing to do with normalizing for equally loud peaks...it's more about adjusting the individual "objects" (that's what Samplitude calls them when you slice up a track into small parts) so that their level is consistent with the intent of the recording.
So....if the vocals have one quite word that was not quiet intentionally, but rather it's just how it got recorded...and during the mix that one word is getting lost, level-wise, you can adjust it to be consistent with the the rest of the track. Same thing if something is too loud...like a guitar string that got plucked too hard on a given note or a snare hit that just sticks out much louder than all the others...
...that's what editing is about, that's what a DAW is for.
Not sure why some folks are "concerned" about doing these types of edits.
You are doing what needs to be done....there's nothing wrong/fake about adjusting levels/EQs/etc.....