This may well be "works as intended", but it seems like it isn't, so I'm reporting it anyway.
In 1.11, potions drunk directly by players act as them doing damage to themselves. Since a player on a team will be on the same team as themselves (obviously), the friendlyfire team option causes damage potions to no longer work if disabled.
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Comments 3
Thank you for your report!
After consideration, the issue is being closed as Working as Intended.
Please note, that mechanics of the game may change between updates.
Things such as graphics, sounds, world creation, biomes, redstone, villagers, and animals may not work the same in current versions.
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Confirmed for 1.19.4 and 23w14a.