It is OK to e-mail editors. But unsolicited e-mail for commercial purpose is spam. Were you writing the editor for commercial/promotional purposes? Was your e-mail specifically solicited?
And you mention courtesy: a lot of people think they can be as rude as they like if they say "please" and "thank you". To them, I have only one thing to say: "Please kill yourself, and thank you for doing it slowly and painfully!"
No, if you e-mail an editor, basic courtesy consists FIRST in determining whether that editor might want to discuss the subject.
And it is pretty self-evident that an editor has no a priori reason to want to discuss any particular site submittal -- after all, if he were interested in that site, he could have reviewed it already! And if he were interested in hearing about possible sites for the category, he could have looked in the submittals for that category! No need to use e-mail for those purposes, and it's pretty selfish and thoughtless not to realize that! No, there's no way to be politely selfish and thoughtless.
For these and other very practical reasons (like the number of psychopaths that have figured out how to use e-mail) I've pretty much stopped responding to any mail that doesn't indicate the writer knows me personally. And ... I'm one of those editors who used to reply to EVERYTHING, and kept a throwaway e-mail box specifically for that purpose.
However, if there's something that DOESN'T fit the normal suggest a site/point out a bad listing pattern of communication, then editor e-mail will usually be welcomed. Something like describing a pattern of problems; discussing a subject the editor has indicated a particular interest in; in other words, anything that treats the editor like a real human with feelings and goals, rather than as chattel to be driven for your ulterior motives -- in otherer words, REAL courtesy, not the empty grammatical forms thereof -- THAT will usually be welcomed, and often get a response.