Parts of it are similar enough to pain killers that some meditators occasionally get into trouble with not going to the hospital soon enough. So the amelioration side of things seems pretty straightforward. We (QRI) recently spoke with Daniel Ingram about this. We still have some followup questions but he's very good at jhanas (incl 4th which is high equanimity) and claims to be an arahant and said that kidney stones (which he has experienced ~14 times) still caused suffering. This is particularly interesting because using deference networks showed us that people report kidney stones as multiple orders of magnitude worse than the next closest thing, which Daniel also claimed unprompted from us.
This doesn't address the core of your concern about utility, but since suffering and utility are both under-specified I'm not sure what a definitive answer looks like.
My experience after several years of daily meditation is that while I am still entirely able to feel pain and act on its message, I often "suffer" over it less. To clarify, instead of what my 4yo does when he gets a bump or scrape (fully inhabits the pain, cries it out, often displays a long-term mood drop), or how I used to handle pain (TBH, similar but less loudly and wetly), my current reaction is more like "Ouch. That sucks. Do I need to make repairs?" and move on with my life. If I'm particularly on my game that day, I might even observe the sensations as the pain evolves over time.
Most clinical definitions of pain that I've seen specify that it has an emotional component. Though exactly which emotion that might be is (as far as I've seen) always elided, I expect it's simple aversion. Equanimity practices seem to be designed to let us choose to experience sensations with less (approaching zero) aversion or clinging emotional content. Without the aversion, it seems you simply aren't experiencing "pain" anymore. This is also suggested when meditation teachers claim that if you can summon curiosity or interest in the painful sensation, you don't have pain anymore. I also keep hearing that aversion and clinging are where suffering comes from in the first place, which lines up nicely with all that.
Based on your comment on Ricraz's answer, "something that is bad for me", I will make a guess at what you mean. Let me know if it answers your question.
Objectively (outside-perspective):
"Bad" requires defining. Define the utility function, and the answer falls out.
Depending on your goals and the context of being hurt, it might be negative, positive, or a mix of both! (ex. being unintentionally burned while cooking, being a masochist, and being burned to protect a clumsy loved one, respectively)
Subjectively:
If you mean negative utility as in the negative valence of an observation, then I would argue that negative valence is a signal telling you how well you're achieving a goal. (this is from Kaj's Non-mystical sequence)
From a multi-agent view, you may have an agent giving you valence on how well you're doing at a goal (say a video game). If you're really invested in the game, you might fuse with that sub-agent (identify that with a "self" tag), and suffer when you fail at the game. If you're separated from the game, you can still receive information about how well you're doing, but you don't suffer.
The more equanimity you have (you're okay with things as they are), the less you personally suffer. Though you can still be aware of the negative/positive signal of valence.
""Bad" requires defining. Define the utility function, and the answer falls out" - Exactly. How should it be defined?
Even though I've only just begun dabbling in meditation, I believe that it is an incredibly powerful tool. I do have one worry though relating to what exactly counts as suffering. If I scald myself, this triggers my pain nerves to fire and it is possible that this produces negative utility, even if my conscious mind is able to maintain complete equanimity?
And while it might produce less negative utility in most cases, it is possible that someone who can achieve equanimity might voluntarily choose to put themselves in situations where they experience far more suffering than they ever would without this ability with the end result being net negative for them. A large part of what worries me is that I am massively uncertain about this issue and I honestly don't have any idea of how we could settle it conclusively.
Some factors that might make us more likely to believe this is the case: