A good point was brought up in that thread:
every time you put any water from an infected aquarium in your display tank, you may be introducing the host-free stage of the parasite. This water could be on your new corals, chaeto, live rock, or the sand you use to "seed" a new sandbed.
Most people don't QT their fish. More than most people don't QT their corals, or their chaeto, or their snails. So it stands to reason, in my opinion, that it should be assumed that just about anything we buy could be a vector for the parasite.
If you wanted to be 100% safe you would quarantine everything wet, but just taking care of the fish should prevent probably 90% of introductions.
about 95% of tomonts (that's a real percentage) excyst within 10 days, so if you can get a week and a half of isolation from fish, there's only about a 5% chance of introducing ich from rock, inverts, or algae
Good luck completely eradicating ich! Even quarantining fish is no guarantee; there's still a chance it can get introduced into your tank from everything else -- and you cannot treat inverts, corals, sand, or live rock with hypo salinity or copper.