Earlier quoted context omitted.
You say: > Anyway, I would be really surprised if die-hard thoughtless style prescriptivists thought that the advice "don't use the passive voice" was meant to apply to participles. Presumably you mean phrases including participles, not participles by themselves. But https://languagelog.ldc.upenn.edu/nll/?p=2922 "The passive in English" says: > The relevance of participles is that a passive clause always has its verb…
> But https://languagelog.ldc.upenn.edu/nll/?p=2922 "The passive in English" says: >> The relevance of participles is that a passive clause always has its verb in a participial form. > So, what are you saying they do think it was meant to apply to, if every passive clause always includes a participle? I'm confused. OK, you're confused. In the general case, an English verb has five forms†: "plain form" [go], "preterit…
When you say "We can be even more specific than that: the verb is always in -en form," you're also contradicting Pullum when he points out that the present participle is also used to form certain passive clauses. An example of this is also given in the Wikipedia article, "I saw John eating his dinner."
So, while I certainly agree that I'm confused, I think you're mistaken. I'm not sure exactly how, because I'm not sure exactly what you're trying to express, but I'm sure that sufficient study of sources like those will make it clear to you.