"ABOK 1408/1409 certainly looks like the Butterfly bend."
Say that again?
Whatever results from a failed attempt at tying the Butterfly Bend will likely look like something distinct enough from the Butterfly Bend.
"One wonders if this Guild should issue a deprecation of [the Ashley Bend], or at least a formal recommendation of some kind that the vulnerability [for a potential mistake in its making] should also be taught, or that the error should be precluded by the motions taught, as in
http://davidmdelaney.com/ashley-bend/ashley-bosun-method.html [.]"
Regarding the Ashley Bend, there is no cause for alarm:
An excellent mnemonic aid exists, which, if adequately propagated by the responsible, can prevent the improper tying of the Ashley Bend, by any tyer, regardless of the tyer's knotting experience or mental prowess:
Left goes UNDER, right goes in from UNDER, right goes UNDER. . . .
"UNDER, UNDER, UNDER for the ASHLEY, ASHLEY, ASHLEY!"
Repeat after me:
"UNDER, UNDER, UNDER for the ASHLEY, ASHLEY, ASHLEY!"
Now, let's have a sing-along:
"UNDER, UNDER, UNDER for the ASHLEY, ASHLEY, ASHLEY!"
Further, along with the above, and instead of propagating the idea that the Ashley Bend is a bad bend because it could be mistied, the responsible can propagate the knowledge that the ABOK #1408 and #1409 knots immediately FAIL to show the characteristic internal crossings of the Ashley Bend (which the Ashley Bend of course does immediately show upon tightening).
"UNDER, UNDER, UNDER for the ASHLEY, ASHLEY, ASHLEY!"
"And if you ever attempt to tie an Ashley Bend, and it immediately fails to show the characteristic internal crossings of the Ashley Bend, then untie it and try again."
JCS