Hi,
The only modification made in the plugin is that check in order to not perform a redirect if there is some data in the POST.
In that case, the plugin return "true", like it already did in various other cases (if you're in the backend, etc).
I don't know why that specific code interact with Kunena but I'm afraid that it can't be the only source of issue.
The fact that the plugin "returns" means that the plugin is doing nothing ; so it does influence anything in Joomla or a component.
docs.joomla.org/Plugin/Events/System#onAfterRoute
So ; yes the HikaShop "no SSL outside checkout" has been modified but the modification is irrelevant.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.