So Treat Condition invokes the counteract rules, and has text: "You can't treat a condition that came from an artifact or effect above 20th level unless you have Legendary Medic; even if you do, the counteract DC increases by 10."
Meanwhile, the Curse trait includes: "A curse is an effect that places some long-term affliction on a creature. Curses are always magical and are typically the result of a spell or trap. Effects with this trait can be removed only by effects that specifically target curses."
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Treat Condition does not explicitly call out curses. Yet at a glance, it seems that most negative effects of artifacts are curses. Moreover, the Legendary Medic Feat also makes no mention of curses, only "an artifact, above 20th level..."
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Another odd bit that's within the Treat Wounds entry:
"The Medicine check DC is usually 15, though the GM might adjust it based on the circumstances, such as treating a patient outside in a storm, or treating magically cursed wounds. ...
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So when and what is supposed to be allowed to try to fight against a curse tagged spell's unlimited duration effect?
Would something as simple as Focus Cathartic be allowed to make a counteract check?
Would Holistic Care be eligible to attempt to remove a curse-trait spells effect?
Since this is the rules forum:
The Curse trait is more specific than abilities that say that they can treat diseases generally.
Saying that it can treat a condition coming from an artifact does not mean that it can treat a condition with the Curse trait even if 100% of the conditions coming from an artifact have the Curse trait - which they don't.
Edit: And the guidance in setting the DC for the general purpose Treat Wounds rules referencing being able to treat effects from curses would be future-proofing. Acknowledging that there may be some circumstances (including homebrew) where a character does have some combination of abilities, items, or spells that lets them use Treat Wounds on a Curse trait affliction.
So...
So when and what is supposed to be allowed to try to fight against a curse tagged spell's unlimited duration effect?
Would something as simple as Focus Cathartic be allowed to make a counteract check?
Would Holistic Care be eligible to attempt to remove a curse-trait spells effect?
When the an effect says that it can fight against a curse effect.
No.
No.
If this was on the Advice forum or the Homebrew forum, I would probably give different answers.
For anyone who digs this up later,
Remaster added an L7 master Occultism/Religion Skill Feat, "Break Curse"
Basically treating disease but instead breaks curses.
It's a bit high level, and the utility of it will vary dramatically w/ how often the party encounters curses and what other tools they have.
That said, it's a great addition, and one I might be in dire need of myself...