You will need to install a user script manager extension to install this script.
Updated script based on the comments preview script from userscripts.org. Completely rewritten, works with new and old design.
There's still room for improvements for the new design:
If you don't care about the new features and just want the old comment preview, you can disable the features in the options part of the script. There is also an option to change the comment sorting for the preview.
This script doesn't work with new versions of GreaseMonkey, use TamperMonkey instead!
Since I'm not planning to add more features, v2 updates will be most likely limited to bugfixes/perfomance.
When autoloading, comments will now be added the bottom of each entry. Comments added by clicking will still be added to the top.
You can change the position of the comments in the options of the script.
I finally added a storing option for the settings. There are two new menu buttons, one to hide/show the sidebar, one for autoloading the comments and images. The script is tested on Chrome and Firefox. Please contact me if you encounter any problems.