I agree the help file isn't crystal clear on that, but by combining what's shown in the help file with what's seen in the dcc-trust dialog window, the -r removes the entry from the trusted list, and has the same meaning that -r has in the ignore tab of the address book. I suspect it would be a good feature request for /dcc trust to also have some of the same switches as the /ignore command has. Such as -l to list everyone in the trust list, with levels and addresses grouped separately, and a -x switch that lets you trust everyone at an address wildcard except for a more specific/restrictive wildcard, or -uN that removes the entry after N seconds.
The dialog says that if mIRC doesn't recognize it as an address, it treats it as a level, which seems to contradict the helpfile saying you can add a nick to the trusted list when it looks like you can only add the address nick!*@*.
So "/dcc trust nick" is adding a 'level' named nick, and not someone using that nick. To trust a specific nick you use nick!*@*. If you use "/dcc trust *@example.com you'll see the dialog window has expanded it to *!*@example.com.
For your example of /hadd, you'll notice that it didn't actually explain all the switches, excluding -s, however scrolling up you'll see it was already defined at the top under /hmake, and is not re-defined for /hadd, /hload, /hsave, /hdel, or /hfree. In the /help entry for Picture Windows, there's several commands which don't define all switches, but it does have a sentence for each of them: The remaining switches are the same as those in /drawdot
