Just weighing in as someone who has submitted next to nothing, but also who dislikes dark patterns generally. I don't think this is the sort of situation where hiding the reality of what has happened makes sense (point 2). If your spamming HN you probably have the smarts to also automate checking if your spam account has been banned (shadow or otherwise) by also automating a check that loads HN when not logged in. I personally, don't see the point in hiding this from a submitting user. I wouldn't like it if it happened to me, and I wouldn't expect it to be an effective technical countermeasure to much spam (though I concede there may be evidence to the contrary on this that represents fact instead of my opinions)
As to point 1, I don't know how hard it would be to expose some of the information. I don't expect the moderation team (hi dang! keep being so awesome!, this isn't even sarcastic, what you manage to do genuinely awes me, I know I couldn't manage to moderate HN.) to have the time to post individual comments about every ban, but it does feel like something that could perhaps be made less opaque. If you know it was banned/auto-dead due to a specific rule, then thats better than just having no idea. With that information I know I would feel slightly less intimidated asking hn@ycombinator.com in an email why my submission was dead/banned, that email goes from "why my did you block my thing" to "I see my submission ran into this rule that has nothing to do with me personally, I just thought it was cool and wanted to either know why, or if my cool thing could get given a second chance" ... which feels a lot less confrontational to me.
I try to think about the "ops burden" with this sort of thing, there may be good reasons why things ended up the way they are, but that doesn't mean things couldn't improve and so its at least worth the discussion from time to time like this, even if the original reasons hold and for whatever reason, the current behaviour is still the optimal one for now.