Got an issue with the latest version pulled from github. I installed it on a recent MediaWiki and a fresh one too. I get the same error in both cases:
Fatal error: Can't use method return value in write context in /var/www/wiki2/extensions/Html2Wiki/specials/SpecialHtml2Wiki.php on line 1357
If I comment out the relevant code the I can reach the SpecialPages.
I don't know if its an issue or not but I can reproduce the error.