When I try to use "Extension:Replace Text" to search and replace in namespace NS_PROOFREAD_PAGE created by "Extension:Proofread Page", I get following error message:
replaceText: Wiki page "Page:Foo.pdf/39" does not hold regular wikitext.
I think the issue is in file ReplaceTextJob.php on line 79 with following code:
if ( $this->title->getContentModel() !== CONTENT_MODEL_WIKITEXT ) {
$this->error = 'replaceText: Wiki page "' .
$this->title->getPrefixedDBkey() . '" does not hold regular wikitext.';
return false;
}