Steps to reproduce:

1. Open a thread with HTTPS, e.g. https://syn-ch.com/b/res/3916547.html
2. Click a >>link that leads to an archived thread\post, e.g. >>3914980

This will redirect you from https://syn-ch.com/b/res/3914980.html#3914980 to http://syn-ch.com/b/arch/3914980.html#3914980 (no HTTPS).