I don’t frequent this community, so please take what I say with a grain of salt, but I’m not seeing many bars/criteria which is what is being requested so I’ll throw in my two cents.
\1. If it is reasonable context or updates the average person would want/need, then it should be allowed.
Examples:
“It’s great the old lady recovered from her fall down the stairs, but unfortunately, a few hours after this article, she fell down again : (”
“She fell down the stairs because the step height was inconsistent, that needs to be fixed ASAP.”
\2. If it is pointed, hostile, or drumming up anger, it should NOT be allowed.
Examples:
“It’s the Radical Escalator Group that weakened stair legislation!”
“She should have been more careful. This is clearly on the old lady.”
\3. If it is dismissive of the good news or tries to make people feel bad for enjoying the good news, it should NOT be allowed.
Examples:
“Sure SHE recovered, but what about the hundreds of stair fall victims who don’t?”
“How does this help anyone?”
“If you don’t check the stairs you use and report bad stairs, this is your fault, and you shouldn’t be celebrating her recovery.”
\4. General negativity that does not needlessly effect others should be allowed.
Examples:
“My grandma fell down the stairs too. Hoping for a recovery”
“My stairs are all messed up too, but sadly I rent, so I can’t fix them…”
“This will likely happen again. We should make sure the needed resources for recovery are available, or the next one might not end so happily.”
I do think the only punishment should be removal and a warning, but I do not mod, so I’ll leave that discussion to the experts.
Edit: formatting x2
On its own, I would call that dismissive. Generally, I would say that “negativity that does not needlessly affect others” is more about adding to the discussion in a healthy but negative way. Personal anecdotes, pushing for future positive action, simple sympathy/empathy, or even the below part of my comment, would be what I would put under this category.
Sadly, I don’t think it is possible to have rigid objective categories due to the subject of this community. But that was my thoughts.