rpm 3.0.3 seems to expand macros within comments. Example:
Having the following two lines
# User-Defined Macros:
# %define <name> <expansion>
in a spec file will lead to an error message:
"Macro % has illegal name (%define)"
This was working ok in rpm 3.0 and 3.0.2.
*** This bug has been marked as a duplicate of 5364 ***