It's definitely not the most constructive/informative post ever, but I personally wouldn't call it spam to be honest.
Your post was deleted because your quoted post was deleted. Did you see my post (you quoted) was anyhow off topic? You suggested something and I was trying to point that was not possible.
I don't think that was the case. I think both our replies got deleted. I don't think my post would automatically get deleted if the post I quoted got deleted. Also, I don't think it's off-topic at all? But whatever I guess. I'm fine with it.
I think it is. I've had some deleted posts also from trying to correct someone's posts and quoting them. I searched the comment I quoted and it was deleted as well. It makes sense to delete both because if not, then other readers will get confused.
On the off-topic, it falls on the mods discretion.