I just installed RE621 and enjoy it a lot, though I have a few things I'm unsure about. I use Firefox 79.0 and Greasemonkey 4.9.
• Trying to install the script from Github by opening it in a tab (as it says in the instructions) didn't work, I'd only get a prompt to download the script.user.js file no matter what I did. I had to download the script and paste the code into the "new script" box to get it to work. Possibly because of this, Greasemonkey won't let me set the script to auto-update.
• Hitting the Back/Forward buttons in the browser makes the script reload on top of itself. I get duplicates of the icons in the header, and so forth. (I understand if this is something you can't fix, but I thought I could let you know just in case.)
• Every time a page loads, it takes ~3 seconds for the page to reshuffle - the parent/child post thumbnails move under the searchbar, the image moves up and to the right a bit, the arrows on the navbar move inwards a bit, some tags are bolded, and so on. Is there any way to disable the layout changes? I prefer to have the parent post thumbnail where it usually is, and the "reshuffle" is kind of an eyesore.
I feel mean complaining about a passion project like this, which is otherwise very good, so I want to emphasize again that I actually really enjoy RE621! :p Thanks!