It is not a feature of the level. It's a feature of some of the engines the level was officially playable on.
Ah, that chestnut. Fair enough: in that case, the level should probably spawn ABCABC, because that's what NL does. I'm keeping my vote as the second option though, because that is genuinely what I feel would be best, and I don't think overlapping entrances is unfair. It would be
better if there a visible way to represent them, of course, and here are some suggestions (some of which I'm sure I've made previously):
1) Make overlapped entrance hatches a different/darker colour.
2) Have spawning indications in CPM
3) Include spawning number/order/number of hatches as panel info (this would take up more space on the panel, but frankly it could probably do with a bit of an overhaul anyway - I'm not pushing this as an idea though, because there have still yet to be decisions made regarding the menu thing!)
4) Invent a character called "Helper Cat" who pops up (in a similar way to the old Microsoft Office Paperclip dude) and lets the player know stuff they need to know about the level

I note that you made a proposal then that hatches should have helper indications "A", "B", "C" etc to indicate order (presumably at the start of the level, at the same time the arrow for facing direction is displayed), which would not only solve the unfairness issue here, it would address the fact that hatch order is always hidden information when there are two or more hatches.
Thanks for reminding me! And yes - that's a good point: in a multi-hatch level, there is
currently no way to know which hatch will spawn first, not to mention the order.
For example: a level could have 27 hatches, none of which are overlapping, so it's technically "fair", but the player has no idea which hatch will spawn next until all 27 hatches have spawned. Granted, a level with this many hatches may well be skipped
because it has so many hatches, but yes: maybe having a spawn-order-indicator would remove the unfairness of overlapping hatches whilst also informing the player of spawn order.
some authors would be okay with their content being flagged as unfair; others would say "Fine, you win"... the likely end result is the same as if namida were to outright block release of any levels that don't meet his fairness standards... it's not the solution I want to see happen.
Me neither, for sure. I'm in favour of freedom of expression for creators being preserved as much as possible.
Can you elaborate a bit more on why "unfair content detection" would result in the same scenario as outright banning of unfair content, please? I'm not sure how it would be the same...

Personally, I'm in favour of an "unfair content warning" system: it allows creators to make whatever levels they want, and players can simply skip any levels that feature a warning (if they want to). The benefits of this seem quite extensive: it means that players won't skip an entire
pack because of one "unfair" level - they can just skip that level, as well as being a way to put an end to (or at least limit) the recurring conversations about whether levels should or should not contain controversial content.