On my survival world, I was slain in a cave by falling, so I re-spawned and sprinted off to find my house. When I located it, I identified a Pillager Scouting Party spinning endlessly in a river next to the house. Anyway, I rushed inside from excitement and grabbed my inventory to kill them.After returning to the surface, I took out the two Crossbow Pillagers and received nothing, leaving the Banner Pillager who had an Axe. After killing him, I received the "Ominous Banner". Since I've looked up nothing about this new update, I searched up the banner on the wiki. It said that placing/hanging the banner will not cause Pillagers to attempt recapturing it. After leaving the banner in my room after a good 10 minutes, I received the "Bad Omen". It says on the wiki that I can only receive "Bad Omen" by living within a Village, which I am sure that's not the case. Anyway, after a good 20 or so hours it's still affecting me infinitely. I have slain about 7 or so Pillager Captains, and they keep coming back.
As Hexalobular said, drinking milk removes the omen and prevents raids. I carry a bucket of milk with me at all times. It is a nuisance sacrificing an inventory slot, but well worth it, since I don’t have to go looking for a cow after killing the guy carrying the banner.
By the way, where did you get the information about having to live in a village in order to get the bad omen effect? The Wiki does not say that to my knowledge. The way it works in my experience is:
1. You encounter an illager patrol
2. If one of the illagers in the patrol is carrying a banner and you kill him, you immediately acquire the bad omen effect
3. If you enter a village - any village - with the active bad omen effect, a raid bar appears at the top of the screen, the villagers flee to their homes (well, they are supposed to) and a raiding party spawns and heads for the village.
I think that the more banner-carrying illagers you kill, the more severe the raid will be. The process has nothing to do with where you "live".
"The banner dropped as an item on the ground will attract illagers from a pre-existing patrol, who will try to pick it up and start carrying it. AFAIK it doesn't influence illager spawning, just makes whatever illagers spawned naturally to pathfind to it.Hanging/standing (placed) it should have no effect whatsoever."
You get the effect, and a symbol in the corner of the screen to show you have it, when you kill the captain.
But it shouldn't do anything unless you enter a village while it's active.
So as long as you stay away from villages you should be able to just ignore it.
And the thing you found on Reddit sounds like what you said earlier about the Wiki, that displaying the banner should have no effect (except in Bedrock) but something seems to have been going on with all your patrols. I don't know what though. Whether it's bugged or if you just had bad luck.