I often find it helpful (if not downright necessary) to search through mIRC's full versions.txt file, which contains all the per-version changes throughout the years. Searching for "/dcc trust" in that file yields the following entry:

Quote:
46.Added /dcc trust [-r] <on | off | nick | address | level>
to add/remove items to DCC trust dialog, and $trust(N) to
return items in trust list.

Based on that I would guess that -r simply allows you to remove an entry. The "level" part is a reference to Access Levels (a topic with its own helpfile page), as confirmed by the "Trusted Users" options dialog (alt+o -> DCC -> [Trusted]). I'm not entirely sure how that works with this command though, since nicknames may be valid access levels as well (and vice versa)..

Saturn, QuakeNet staff