This site is driven by two keys, like the machine it came from. Reading: j and k scroll, d and u move half a page, gg goes to the top, G to the bottom, H and L switch windows, ? opens the help. Space is the Neovim leader and handles content: Space then h home, r research, p projects, g gear, a about, / tags, or Space then a digit to jump to that window. Home is the tmux prefix and handles windows: Home then c opens a terminal, Home then & closes a window, Home then space goes to the next one. While focus is on the keyboard, h j k l move between keys and Enter opens one.
Something else is reading your keys
One keypress scrolled the page twice, so a browser extension is running its own bindings alongside this site. The site already stops propagation as early as a page can reach, but an extension that registers before any page script still wins. Only an exclusion rule inside that extension can fix it:
h j k l d u g G H L r p a c w n q x z ? / & 1 2 3 4 5 6 7 8 9 If the remapping happens at the OS level (Karabiner and the like), this site can do nothing about it: the substitution happens before the browser ever sees the key.