Back 20 years ago, our police forces didn't like people using sound moderators for all the reasons you listed, center fire sound moderators were almost unheard of.
These days it's expected that you will use a sound moderator for hearing protection and in some cases landowners wouldn't let you shoot on their land if you were not using a sound moderator. The major benefit with center fire sound moderators is the kill in recoil, making a .308 shoot like a .410.
The world is a crazy place, thats for sure. Both you and I know that a sound moderator makes little difference to a 'hit' man, who in all likelihood would use a shotgun any way or some other form of killing and lets be honest, it's not hard at all to produce a sound moderator in any half equipped workshop. I would bet I could produce one in half a day in my garage, using aluminium tube, of two diameters, washers and some plumbing fixings, give the whole lot a spray with black paint and you would have a half good sound moderator. The crazy thing is in the UK that would be legal, and it would be legal to use it on a shotgun or an airgun but not a firearm unless you registered it with the police and had it added to your firearm certificate!
Have a gander at this : hushpower.co.uk
You may notice that boxes of them appear on the gun shop counters: Jackson Rifles - rimfire and air rifle silencers
Or the Parker Hale MM1
And talking about the MM1, I took mine apart for a clean:-
What I do is smear the crown with "copper grease" to protect it from corrosion, all the crud simply wipes away.
Here are the internals, not cleaned in many years. I honestly can not remember the last time I took this thing apart but I'm sure I have at some point (baffles are just like the engine block freeze plugs) :
Wiping out the inside of the moderator (I'll also scrub it with a 12 bore bronze brush). Robla Solo Mil is great for cleaning all the crud off, in fact it eats powder residues for breakfast.