It is not mean spirited to suggest that if someone has a Don't Do This sign on their property it would be a little odd for them to do it on other people's. I mean, the sign says "If you don't have a LEGITIMATE reason to be here, please go away." Who is to say knocking on doors asking for debris is legitimate business? The homeowner, obviously; but it isn't mean spirited to suggest other home owners may feel the way Knitterly does. She wants people to go away ... maybe they do, too.
I want sales people to not ring my doorbell when my baby is sleeping because it interrutps her naps and frequently means she won't go back down.
I hope I can make a few things really clear:
1) If I don't have my "don't ring the bell" sign up, the bell is fair game (to all but solicitors - especially that same lawn care company who keeps harassing the entire neighbourhood).
2) You can't read the sign from the door.
3) If someone had a sign on their lawn or door or anything, I would not bother them. Period. I would respect their privacy.
4) I am not the neighbourhood grouch. I am also not the only person in the neighbourhood who is flat out annoyed by the sheer quantity of scammy salespeople we get flocking through here.
I really don't see my request to please not ring my bell because the baby is sleeping as conveying that I never want to meet my neighbours. It's not a "do not disturb" sign. It's an "I don't want to buy your junk" and a "please for the love of deity don't wake up my sleeping kid" sign. I would not find it at all strange if a neighbour with a sign stating that they didn't want to be disturbed
because their baby is sleeping came up and knocked on my door during a non-nap hour. I wouldn't find it strange at all. But then, I might, myself, be a little strange. The jury's still out on that.

(quote tree trim)
I got the impression that snowdragon's point about being "not pleased" was related more to the act of knocking on the door at a house with a "No trespassing" sign than to the request itself. She has clearly indicated that she doesn't want people coming on her property by posting a "No trespassing" sign. Therefore, it makes sense that she would be annoyed if someone ignored the sign to knock on her door anyway, especially if their request/reason for knocking was purely for their benefit rather than hers. I.e., there's nothing inherently wrong with making the request, but it's wrong to ignore a home-owner's signals that uninvited door-knockers are not welcome.
I got the same impression. And I wholeheartedly agree that one should not knock where one is clearly not welcome.
And if snowdragon lived in my neighbourhood and I saw her no-trespassing sign, I would certainly not trespass, no matter how temptingly the tree branches might lay on her yard.