DERSIG BIP looks great to me, just a few nit-picky changes suggested:

You mention the "DER standard" : should link to
http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf (or
whatever is best reference for DER).

"this would simplify avoiding OpenSSL in consensus implementations"  -->
"this would make it easier for non-OpenSSL implementations"

"causing opcode failure"  : I know what you mean by "opcode failure", but
it might be good to be more explicit.

"since v0.8.0, and nearly no transactions" -->  "and very few
transactions..."

"reducing this avenue for malleability is useful on itself as well"  :
awkward English. How about just "This proposal has the added benefit of
reducing transaction malleability (see BIP62)."


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Gavin Andresen