> Feels like saying "soreness is your muscles recovering from damage and you should avoid it."

Except this is an analogy not a true comparison of the systems. The act of growing muscles is due to muscle damage and regrowth (to really handwave), and that action causes soreness. It’s not cumulative damage to the muscles, ideally it should heal in between. The same experience is not true for skin. You’re not “improving the health” of your skin by being tan, and we know that damage to the skin is cumulative.

The health benefits of being in the sun seem to be a combination of mental-health (sun=happy) and chemical-release when skin is exposed to sun (eg vitamin D). This seems more like “certain side affects of sun expose are positive to the overall body, despite the growing damage to the skin”.

Agreed that it is an analogy. I'll go farther and agree that I could flat be wrong! :D

In the analogy, though, I do know people have a hard time distinguishing between pain and soreness. Such that it is not uncommon for people to exercise too hard and trigger pain, which will slow them down. As such, I expect that sun exposure is likely the same. I even agree that it is probably easier to jump over any threshold that there may be and to get too much sun. I have a hard time thinking any darkening of skin is a sign of damage, though.

I also think it is tough to distinguish between damage versus wear. Which, is probably just my not liking the language of "damage" here. Do we say that guitar players have damaged their skin to build calloused finger tips? (Genuine question.)

The skin suffers (permanent?) damage from the sun. Not wear. Not darkening. Not “kinda in pain that does away”. Damage-like-negative-connotation-damage. (Yes it also tans and wrinkles and calluses).

This damage is mostly ignored until it manifests as cancer of the skin. Then it’s too late to undo the damage, and its treat-the-cancer time. But you can use tools at dermatology offices to see the damage more clearly, and you can take action to slow the damage (eg Sunscreen). But it’s absolutely suffering damage that one day may manifest as potentially lethal cancer.

I don't want to dig out the reference, but it seemed pretty credible when I read it.

It states that while it is true that people exposed to the sun get skin cancers more often, their outcomes are also usually far better.

So are their outcomes to all other forms of cancer. Thus, overall, the benefits are substantial.

This is not to say you should go out and lay in the sun for hours and get your skin dark brown - instead, it is about not being afraid of normal and regular sun exposure. It is good for you.

Things that mildly damage cells are not necessarily bad for you. They trigger apoptosis, a renewal of these cells. This is why fasting is beneficial, why exercise is beneficial, and why challenging your cells is beneficial. Many of the famous mud and water treatments that help arthritis have waters that are ever so slightly radioactive (well within safe limits but far higher than normal background radiation) for example.

You get new and more resilient, and better cells.

Except we have hard proof that tanning your skin raises your risk of melanoma. And, in fact, tanning regularly is more harmful than getting burned rarely.