I just think some skills are more special than others. Like you said, +Rgen items are much more desired to wish for. So why would anyone ever wish for Healing? :-)

(Yes, I understand that sometimes someone might want to. But it's not IMHO a good enough reason to change this deliberate rule.)

I actually never found healing remotely essential, contrary to popular opinion. Must be something to do with my playstyle. So it wouldn't seem unbalanced to me if it were a wishable skill. I covet alertness much more though--although there are a few other skills almost on par with it that are sometimes worth a wish.

I'm with The Creator. I don't think that PC should be able to wish for really anything. Skills in ADOM is the one thing that makes r/c combos really different. I'd rather extend list to include other crucial skills: concentration (instead increase max PP, restore them all show all secrets in LoS), cooking (get all your food cooked), did weakness (not really sure, since I'm playing ADOM a long time I'm not against even punishment to PC's St), detect item status (act a blessed scroll of identify), food preservation (bless all perishable food).

My view, if you got a wish (which is happening in the most of my games at least once), spend them on anything. But not on making your r/c combo similar to others.

I believe there are more significant skills than alertness and healing, when you consider TB's justification.
I wholly agree with Ln about the healing skill. If I were to get a wish in the early stage of the game, I'd rather wish for gardening or herbalism than healing.
In the long term, the latter provides fewer benefits simply because herbs can be used on demand to restore large amounts of HP and you gain a source of toughness, willpower and dexterity training.
If I really needed regeneration, healing would once again be my secondary choice because of the clear superiority of items granting regeneration.

As for alertness, I guess I can agree with TB to some extent.
It is a nice and useful skill but after a number of games without it, my conclusion is similar to that regarding healing:
If I had a wish in the early-mid game, there are much better choices than alertness.
Furthermore, in the later game it doesn't really matter anymore, since HP pool covers you in this department.

The only place where alertness has a potentially game-changing effect is the ToEF.
PCs there often are under-equipped and having the wyrm miss you several times due to successful spell evasion granted by alertness, might just give you enough time to put it down.
This however assumes that the skill is developed, to somewhere around 80+.
That is very often not the case with wished-for alertness, simply because it levels up so poorly.

When you consider the above, healing and alertness aren't really out of the line when compared to other skills, especially when you factor in the frequently low starting dice that almost do not improve as the game progresses.
This difficulty in training further stunts the usefulness of these skills when wished for.

Hence, I vote to have both healing and alertness available via wishing.

I thought about this after his post on the previous RFE. In fact, I have come to terms that I some skills being unwishable would be a reasonable system. Including some you have mentioned (Concentration, Find Weakness, Food Preservation). And for the exact same reason you have mentioned -- distinguishing races more and more.

However, this RFE is only about Healing which I find in a weird spot.

1) You can get it from Jharod and wish for Herbalism, but not vice versa, whereas I don't see why exactly Thomas wants the Jharod quest to be more special than the Keethrax quest. They are in my mind equally interesting and provide entirely different benefits to keep each other on the same level.
2) As I said before, it offers quite nothing in the long run as it is easily interchangeable with some items. Most of the skills you have mentioned are more unique and deserve to be unwishable more.
3) No races start with the skill so race balance will not be compromised if it's made wishable.

Agree with you Ln. I learned to play my Necromancers and Mindcrafters with. But several years since I started playing ADOM I hardy could survive even early game with no healing. It's the most obvious straightforward way of getting back your HP. You have to play the game a while until you discover tons of the other ways it offers. I guess that's why TB have chosen exactly healing rather than anything else.
Anyways, by the time you learn to play without healing at all you wouldn't need to waste a wish for it in any case...

I could go either way on Alertness, but I 100% agree that Healing should be wishable. Wishing for rings of regeneration is a way better wish than Healing, for instance, so I see it in no way overpowered.

I'm certainly OK with designating certain skills as unusual and special enough that you have to be the correct race/class to get them.

However, Healing specifically doesn't reach that standard. A great many classes have it, any PC can easily obtain it in the early game at negligible cost (the opportunity to learn Herbalism instead, which *is* wishable), and it is sufficiently commonplace and mundane in Nature that I think it should be possible to learn it.

Personally, I don't think I would ever spend a wish on it, but it might be a very satisfying result for new players.

As an aside, what would be very disappointing and dissatisfying for new players is to wish for healing, intending the skill, and get HP restored; or else wish hoping for HP, and get the skill instead. Therefore I suggest that in the interest of making the game pleasurable for newbies too, a wish for "healing" should just give both: you learn/advance the skill and get restored to full HP. Why not?