Sibilance, to me is the most annoying of virtually all system flaws. I remember my first foray into High End audio was disappointing almost entirely, because there was virtually no female singer who didn't sizzzzzle into the mic, or so I thought.
Extended HF, with no regard to interconnects, speaker cables, GOOD solid state, (which back then was an oxymoron), a cart for the table which could actually track correctly. That sibilance unearthed a vast multitude of problems.
"What's New", by Linda Ronstat was such a dissapointment for a long time because of this. The music, I loved, the rendition of her voice, not so much.
They obviously peaked her voice in the upper ranges; why, to give it more 'presence' I suppose.
There is a device which produces 'tube like' distortions, known as, and I'm no doubt wrong on this, "Aphex Aural Exciter", which introduces tube like distortions onto the recordings. Many female vocalists, Barbara Streisand being, at least at one time, the most visible, LOVE this effect.
In designing some speakers, one of my principal goals was to have NO SIBILANCE ADDED. Sure some recordings sound that way, but a speaker with just a few db of spike in the upper regions, and in the wrong bandwidth, can send most of us running from the room. Again, and I've said it before, a good theology for speaker designers, could be "The best tweeter I ever heard, I didn't."
This should be viewed as, HF's sound electrostatic, not 'dome'.
I'd personally rather have a slight roll off than that nails on the chalkboard sibilance.
"I'll talk, I'll talk, God, please make them stopppp!!!!!!"