I cannot expand a macro after underscore, as the following sample shows in detail:

#+macro: xxx A
* macro bug
_{{{xxx}}}
a _{{{xxx}}}
a_{{{xxx}}}
a^{{{xxx}}}
a{{{xxx}}}
a_A

generates:

_A
a _A
a_{{{xxx}}}
a^{{{xxx}}}
aA
a_A

thx

m