I have had this going on with traffic noise for months now. My AuD hasn’t been able to fix it. At our last adjustment, she said the compression values all looked good.
I’m not an expert, but my guy told me the hissing is common with compression. I don’t fully understand what that is but he told me because I am a musician he isn’t using it and I am getting no hissing except when I turn my volume up above zero to 3 or 4 on my Oticon ON app.
You’re ignoring this member’s posts.

Over the years, you tend to treat it as common practice, and perhaps learn to ignore it, this leads to a more ambiance, and usually less conflict…. Most severe/profound folks are excluded in general from this hearing society, they want answers immediately if not sooner, after maybe years of isolation & frustration, forum etiquette and protocol tends to go out the window, especially from new or less experienced members, also if you consider (Sudden Sensory Neural Hearing Loss) these folks are frightened, need reassurance, and perhaps out of sheer panic they might hijack a thread, so as a general rule of thumb we tend to ignore… YMMV, my 2 cents worth