Some UX & UI issues I've come across and some suggestions to address them

issue: menus are not always immediately apparent

suggestion: style menus like sidebars (outlines and backgrounds)

issue: user menu elements on mobile are jammed against left edge

suggestion: add left padding

issue: content and comments are too narrow on large/wide displays

suggestion: add option to set min and max widths relative to viewport (CSS VW)

issue: main menu (from hamburger button) elements on mobile/narrow displayed as block is unsightly

suggestion: elements should be inline-block until they cannot fit on one line

issue: comment action icons are unnecessarily hidden

suggestion: show all comment icons persistently (could be grouped as [up/down/reply] on left, [message/flag/block/fav/source] on right; could be a user profile option to show/hide additional comment options persistently)

issue: message notification (bell icon) often indicates unread count when all messages are read

suggestion: fix

issue: auto-refresh on posts causes elements to move down as reading when scrolled

suggestion: implement option to disable auto-refresh OR move scroll position down correspondingly to total height of dynamically loaded post elements

issue: (if above feature implemented) must refresh page if auto-refresh disabled

suggestion: add soft-reload button (reloads posts)

issue: [subscribed|local|all] default from user profile doesn't work (always selects local)

suggestion: fix

issue: no function to block a specific community from your feed

suggestion: add function

issue: notifications view has no stateful awareness of viewing mode [unread|all] or [all|replies|mentions|messages]

suggestion: add stateful awareness to enable browser <|> navigation

issue: replying to inbox comment/message does not display after submitting reply

suggestion: display reply to comment after submitting reply

issue: [show context] from inbox comment does not display immediate parent comment

suggestion: [show context] from inbox comment should display immediate parent comment

issue: when viewing context from comment on a non-local instance, you are not authenticated and cannot reply from context

suggestion: implement cross-instance authentication OR link to context in the currently-authenticated instance

issue: [next] buttons have no stateful awareness (displays an empty page when clicked from the last page in a set)

suggestion: [next] should be statefully aware of page and be disabled when viewing last available page

issue: when inbox messages appear as a notification, there should be a button to mark them as read

suggestion: add function

issue: inbox messages are only marked read when explicitly clicking [read] checkmark button

suggestion: messages should be marked read when replying or navigating to context

Hope this helps make some improvements to the UX! :)

EDIT another one while I'm thinking of it: it would be nice for the top toolbar to be fixed at the top so you don't need to scroll back up to use it.