Let's define this category once and for all, no more questions and misconceptions, with respect to it's previous rules

I will just go by a set of rules, with which we point out the flaws and agreement

1. No damage of any kind (environmental, enemy, self, etc) - Obvious, doesn't need change.
2. Proceed through the "intended" gameplay path - We must go through the level as it is the main path with no side areas, or with them, but with a few exception, like the lava lake (skips 1-3), lukki area, (skips 5-6). I aslo need to mention the tree. Since it's not really where you need to go, and we do it for the worm egg (vision) and greed curse (a lots of money with a negative side effect).
3. No skipping levels - previously aforementioned level skips not allowed, now Holly Mountain digging, allowance or not. If allowed, where can we dig, only towards the exit (lower open entrance, or hm collapse trigger), or anywhere but not sideways, because semi-skip.
4. No wands dropped by the ghost (gold drops are ok) - Obvious.
5. No Invisibility of any kind - Obvious
6. No teleporting of any kind except the Holy Mountain portal. - Obvious, but the side puzzle or a stage puzzle like the snowy depths eye secret and hiisi base eye room contain their portals. if rule 2 is the second option, it can be allowed. If it's the first. only the eye secret from the snowy depths. Swapper mage attack is allowed and getting randomly swapped via hurting the swapper mage.
7. No Ambrosia or Glass Cannon - You can get stained or get inside the Protection From All fields from the SQ biome modifier, but not get hit while under the effect of protection from all, aka BLOCKED message is forbidden.
8. No "rare" alchemy, even if found by luck - This is the draught of midas, it's the only thing which can change a favor in your side, It's funny, because it implies the infinite money is the problem, yet, the current record held the same issue with pheromone ghosts. Shall we ban this as well? It won't affect the previous runs as it is, but the future players won't have to use the older version of the game.
9. Polymorph is allowed as long as you don't take damage during its duration - Weird one, but it's a very Noita mechanic, let's add this, you are allowed to get hit by a non-damage polymorph attack. Since it did happened before and was considered such.

Make sure to point out the flaws and add what would you like to see, implement.

By the end of it we should have a shorter, but more defined version of true hitless%

The majority of the rules are quite clear aside of the part that pertains to the path. What is the "intended" gameplay path exactly? And intended to be played such by whom? Does the intent here is to not use the snowy depths drop or the lukki side biome? That would be the case most likely, as that would also skip zones [see the skip rule], while still being an intended way to travel [a free-to-access location, quite blatant and easy to notice]. Hardpossession here brings a good point of the holy mountain zone. Where does the intent lie? Can you dig through the holy mountain at all? If so, towards the collapse point? Around it? Digging out of the mountain isn't exactly intended per say, I would venture a guess to say the intended way is to go through the collapse point. Though, who knows. As a fan of grey line treading to gain as many advantages as possible within the confines of rules, not a fan of these particular ones. Big risk of abuse, lots of chances to off your run completely accidentaly. Hoping for some clarification.

Other questions to the rest of the rules:

What is "rare" alchemy exactly? Does it only relate to Alchemic Precursor and Lively Concoction? Or are other liquids [diminution, healthium etc.] considered rare alchemy as well?

If stained by a forbidden liquid - ambrosia, invisiblium, lively concoction, healthium or under the effect of the protection of all from e.g. the sun quest is the run invalidated immediately? Even if the use was completely accidental? Or is the run allowed to continue regardless, even if no clear use was observed [hard to tell/moderate as even a periodical use of invisibility would in high likelihood affect enemy AI pathing, thought it is more obvious with ambrosia, as taking a hit would mean it was clearly used]

And in regards to the above mentioned rule, does the poly-portal trick for invulnerability apply? It should be assumed than any and all forms of invulnerability through glitches or game mechanics should fall under the same "No using invincibility to not take damage" umbrella and the rule should in my opinion be renamed to such.

No teleporting of any kind except the HM portal - does this also apply to the snowy depths eye puzzle, hourglass room or some new techniques of recoil/pull travel such as the hookbolt? The latter I'd assume no, since recoil was never banned to begin with, but the former two do. Albeit disappointingly, since the rule seems to have only intended to restrict movement, also caused things such as restricting other avenues of gameplay completely unrelated with movement.

Should the rules be systematically changed in order to encompass the newest strategies and metas? Some of the current rules do this, theme of which is being fairly outdated, and that, since then, in turn created new "strong" items/perks/spells for the category - see GC ban or precursor ban. Both are arbitrary, are just replaced by other popular means of damage/money gathering and to a person with no prior knowlege of the genesis of this category don't make sense. It was created as a commemoration of the first recorded hitless by McQueeb, at the time of which many things were different. These exclusions don't, in my personal opinion, create any semblance of, at the present day, rational balancing. Though my opinion is just one of many. Would like some insight on this one from others

The rules have been updated as of 13th November 2024. They feature less arbitrary bans on certain strategies, clarifying some discrepancies and also making it more speedrunner-friendly. While they are longer than before I hope they are much more clear.