>From the current description, it's not clear that if a specified macro isn't found, an exception could be suppressed too. I had to find this out by running an experiment. So, I think the documentation should be updated.

<tal:block metal:use-macro="${macroFileName}/pageSpecificHeadPlaceholder" tal:on-error=""></tal:block>

I've picked up this trick from ASPX files I've recently had to maintain. This allows me to specify page specific additions to the head section within page macros.