the text which is passed in the replaceVariables
function is only the text
actually contained within the template (not the complete article with all
included templates), so it should be ok to have the same function call there
too...
If, for example, an extension uses that hook to add text to the
beginning of every article, putting the hook in replaceVariables as
well would result in the text being added in the middle of article
too, wherever a template is used.
On the other hand introducing a new hook call
'ParserBeforeStripTemplate' or
sth might be the safer way and wouldn't break existing extensions for sure,
and if you want template replacements too (which I'd reckon most extension
writers would want) you'd simply have 2 hook pointers pointing to the same
function 'My_ParserBeforeStrip'...
That would be much better.