I don't check "Worst Nodes" that often, but I have noticed recently that the majority of the "Day" and "Week" lists have been spam: I did check yesterday (around the time I posted) and there were 8 in the "Day" list and 6 in the "Week" list; checking again just now, it's 6 and 6. The Reputations of the spam nodes range from -3 to -6.

My original thought when suggesting exclusion from "Worst Nodes" was that this section could actually reflect what it was (at least in my opinion) intended for. Your comments bear this out to some degree: a "thank you" with an accidental (or even malicious) downvote, with a Rep of -1, is not going to show up when you look.

Anyway, we appear to be in agreement about "Reaped" spam. Prior to consideration, I would assume that they're treated as any other node; that would fit with your current usage of checking for nodes requiring consideration. When considered with a "Spam" button, as suggested by BrowserUk, or by any other mechanism that flags them as spam, I was suggesting that would also prevent them from appearing in "Worst Nodes".