Thread:Extension talk:ImageMap/Extension ImageMap with Extension Header Tabs/reply

ImageMap is very simplistic, and it doesn't send the contents of the tag to the parser. Instead, it reads line by line, interpreting each line and generating links as needed.

It validates each link by looking if the link target is a valid page title (for internal links). If not, it throws that error.

There's no way to insert a parser function or even a Magic Word in the content of the link because of this. You should probably open a bug report for this.