I just tried isolating the hypothesis sidebar in the source code (f12 on Windows) And by toggling one setting "visibility:hidden" I was able to get full access to the sidebar.
Then I downloaded A CSS Injector extensions and added these rules to the extension:
.sidebar-collapsed .sidebar-frame{
/*visibility:hidden*/ }
:not(:defined):not( faceplate-auto-height-animator,faceplate-dropdown-menu,faceplate-expandable-section-helper,faceplate-hovercard,faceplate-tracker ) {
visibility: visible!important;/
}
Now, whenever I activate Hypothesis on Reddit, the sidebar appears as expected. It's a simple hack that could be added to the Hypothesis CSS to make sure that it is visible.