Yes, the verb "is" in "Passive voice is painfully boring to read" is in the active voice, not the passive voice. But umanwizard was not saying that "is" was in the passive voice. Rather, they were saying that the past participle "made", in the phrase "the points already made", is a passive-voice use of the verb "make".
I don't know enough about English grammar to know whether this is correct, but it's not the assertion you took issue with.
Why am I not sure it's correct? If I say, "In addition to the blood so red," I am quite sure that "red" is not in the passive voice, because it's not even a verb. It's an adjective. Past participles are commonly used as adjectives in English in contexts that are unambiguously not passive-voice verbs; for example, in "Vito is a made man now," the past participle "made" is being used as an attributive adjective. And this is structurally different from the attributive-verb examples of "truly verbal adjectives" in https://en.wikipedia.org/wiki/Attributive_verb#English, such as "The cat sitting on the fence is mine," and "The actor given the prize is not my favorite;" we could grammatically say "Vito is a man made whole now". That page calls the "made man" use of participles "deverbal adjectives", a term I don't think I've ever heard before:
> Deverbal adjectives often have the same form as (and similar meaning to) the participles, but behave grammatically purely as adjectives — they do not take objects, for example, as a verb might. For example: (...) Interested parties should apply to the office.
So, is "made" in "the points already made" really in passive voice as it would be in "the points that are already made", is it deverbal as it would be in "the already-made points" despite its positioning after the noun (occasionally valid for adjectives, as in "the blood so red"), or is it something else? I don't know. The smoothness of the transition to "the points already made by those numbskulls" (clearly passive voice) suggests that it is a passive-voice verb, but I'm not sure.
In sibling comment https://news.ycombinator.com/item?id=44493969 jcranmer says it's something called a "bare passive", but I'm not sure.
It's certainly a hilarious thing to put in a comment deploring the passive voice, at least.