it was best not considered
The examples in the question are using "best" with forms of the verb "consider", while Martin is using [considered] / [not considered] as an adjective.
From Kate's comment, "You had best close that door" refers to the verb - to the action of closing it.
If we wanted to refer to an adjective, we could say "That door is best closed", or borrowing Martin's style and tense, "That door was best [not open]".