[BIP-119] Reword section on fungibility in motivation

Author: JeremyRubin

bip-0119.mediawiki

@@ -43,9 +43,9 @@ Covenants are restrictions on how a coin may be spent beyond key ownership.
 This is a general definition based on the legal definition which even simple
 scripts using CSV would satisfy. Covenants in Bitcoin transactions usually
 refer to restrictions on where coins can be transferred. Covenants can be
-useful to construct smart contracts. As covenants are complex to implement and
-risk of introducing fungibility discriminants they have not been seriously
-considered for inclusion in Bitcoin.
+useful to construct smart contracts. Covenants have historically been widely
+considered to be unfit for Bitcoin because they are too complex to implement
+and risk reducing the fungibility of coins bound by them.
 
 This BIP introduces a simple covenant called a *template* which enables a
 limited set of highly valuable use cases without significant risk. BIP-119