I have some more information on the cause of this bug. It turns out that it is an unintended consequence of the recent BVAR and KVAR changes. The parser used be make-docfile is very simplistic. It assumes that when it sees a DEFVAR_PER_BUFFER it can start looking for the documentation after 2 commas. This assumption is no longer valid because of the added comma in the usage of the BVAR macro.
The following patch appears to fix this problem.
<patch> === modified file 'lib-src/make-docfile.c' --- lib-src/make-docfile.c 2011-02-09 00:30:33 +0000 +++ lib-src/make-docfile.c 2011-02-21 09:39:03 +0000
@@ -815,7 +815,7 @@ if (defunflag) commas = 5; else if (defvarperbufferflag) - commas = 2; + commas = 3; else if (defvarflag) commas = 1; else /* For DEFSIMPLE and DEFPRED */