Almost entirely harmless, but when a domain is setup with a "already active" interface, Virtualmin seems to want to control the interface anyway. Pre-active interfaces ought to be left alone, entirely.
The above message is what I got when I deleted a test domain which had been setup on a pre-activated address.
It also indicates that Virtualmin doesn't deal with "range" network configurations (which is fine--as long as it doesn't try to remove them).
Status:
Closed (fixed)