The hex stickers used for category icons are so large they force more white space into the category list. I can only see three categories on my screen. If they were half the size they'd be no less readable, increase the number of categories visible at once, and give more balance to the layout compared to the topic postings on the right. A quick CSS tweak to make the hexes match roughly the personal avatar sizes can do this:
I think that generally the pictures are too distracting: they're big and with very saturated colours, which definitely draws the eye but since the logos are hardly self-explanatory the whole experience is quite confusing. Similarly the round avatars on the discussion list are too distracting. I believe muting all these images with some transparency/desaturation mask would make the layout much more balanced and the actual content (titles, headers, navigation) more easily accessible.
Not experienced with javascript, I can't help as much But I think we can have the stickers in one area in like a honeycomb kind of arrangement, and let the honeycomb be fixed during scrolling, so the topics will be the ones that will change
Thanks for the feedback...we've configured it per the recommendation of @geospacedman. Let us know if anything else is making it hard to engage or bugs you!