Hi @davil2008 @wpkube –
I see it’s been a few days since this was updated, but we had a client that may have been seeing the same problem and got a bit further in identifying it. We were getting PHP memory errors regardless of settings – a 5 GB PHP memory limit wasn’t enough to get the ‘You can also subscribe without commenting.’ link working.
In our client’s case the issue is specifically when the Yoast SEO plugin is active. We were able to reproduce this with a default WP install by installing Subscribe to Comments Reloaded and Yoast SEO. Clicking the link for ‘You can also subscribe without commenting’ caused the page to spin for quite a while before erroring with an out of memory error.
I’m not sure if Daniel here had Yoast SEO installed or if this is something the plugin author can easily troubleshoot, but hopefully this helps.