Ah, you're remembering one of our campfire sessions in which I recounted pitching my Lean 3 on the thick bed of Canadian moss... a veritable mosquito factory!
Right story, wrong location. However, there IS always a story since every pic is worthy of a thousand words.
Despite appearances, where the Lean 3 is pitched in this pic was largely devoid of moss and was mostly bare rock. Also, you have no doubt noted that the "open" end of the lean-to shelter is pitched towards the woods versus the lake. I may be dumb but it was getting very windy. Trust me, I had learned my lesson at that earlier campsite!
Now this island has a very fine location for a campsite. Sadly, this WASN'T it. Unfortunately, the "good site" was supremely trashed-over. As we were chased off the lake by wind, we needed someplace to pitch our shelters and, under the circumstances, this was the best we could manage. It seems we were relatively close to the Ontario/Manitoba border and the First Nation settlement located just on the other side. The once "good" site on this island had long since been transformed into "party city paradise" for those folks long ago. Since the only "flat" spots on the island had TONS of garbage lying on them, we made do with an inferior location further down the island. Any port in a storm, eh?
Other than one boarded-up fish house and one abandoned snowmobile (wrapped in plastic & left on a rock in the middle of East Lake), I don't recall seeing ANY other signs of humanity (& certainly NO humans) during our entire 2 week jaunt through the Opasquia wilderness. The nastified campsite we discovered here was truly an anomaly but a particularly obnoxious one. Of course, that observation might be a "comparative" sort of thing; all the rest was simply pristine wilderness at its finest.
I'm pretty sure there is a pic coming up which better illustrates the story you are thinking about, TomT. I believe I entitled it, "Prisoner in Mosquito Hell" or something like that. Bottom line: your premise is right... thou shalt not set-up a floor-less lean-to shelter on a bed of Canadian moss, a veritable incubator for the mosquito masses. That episode (still to come) became yet another lesson in the book of learnings, entitled: "What NOT to do in the Wilderness!"
Fortunately, this particular set-up was pitched over bare rock. While those legions of buzzing beggars are resourceful and capable of many dastardly tricks & surprises, spontaneous generation ain't one of them.
Later,
Jimbo