Facebook Post Screenshot
Firefox add-on for saving Facebook posts as images

Get it now from Firefox Add-ons website See the changelog
Add-on adds a new option in each post's menu to save its screenshot (with all replies expanded). There is an option for anonymization. Large posts are split into multiple images.
Facebook Post Screenshot is a Firefox web extension to save Facebook posts as images. Add-on adds a new option in each post's menu to save its screenshot (with all replies expanded). Screenshot can also be anonymized (profile pictures blurred, names replaced with identifiers like "OP", "Profile 1", "Profile 2" and so on). Large posts are split into multiple images each at most 8192 px tall (this can be changed in options up to 16000 px).
The code is open source and available on GitHub. If you're interested, check out also my other projects.
Star Issue Follow @hckr
You can file bugs and suggestions in the issue tracker on GitHub. Facebook changes the interface from time to time which causes the add-on to stop working partially or even in full. Instead of giving a one-star review, you might consider filing an issue – I'll surely try to fix it in my spare time.

Changelog

Version 1.10.0
Add opening of the add-on page on update (can be disabled in options)
Add option to capture only the post, without the comment section
Experimental: watching a group and capturing new posts (without the comment section)
Small fixes and refactor
Version 1.9.0
Add options to select relative path for downloaded screenshots and whether to provide a file chooser
Add help tooltips in options
Fix problem with browser_action popup sometimes not repainting properly on show
Version 1.8.2
Fix alignment issues in post menu
Version 1.8.1
Fix for previously introduced bug which caused theater view not to show
Version 1.8.0
Add toolbar icon with menu
Change add-on icon
Version 1.7.2
Add link for creating a new issue in add-on options
Version 1.7.1
Add option for more intelligent partitioning of long screenshots
Fix some issues with anonymized screenshots
Fix a minor issue with add-on stopping working until Facebook refresh after an update
Version 1.7.0
Add options for format selection between PNG and JPEG, and for maximum height of a single part
Store options locally using storage API
Fix wrong links treated as profiles in anonymization
Version 1.6.5
Fix issue with OP mark sometimes not showing in the comment section (but another profile number was generated)
Aesthesic fixes
Version 1.6.4
Fixed issue with downloads and Firefox's "always ask" option
Added info box in main window on start of download
Added support for some new reply-expanding links
Version 1.6.3
Use downloads API to download images (a new peermission is needed), which could solve an issue with downloading captured images for some users
Version 1.6.2
Cosmetic change
Version 1.6.1
Fixed bug with some replies not expanding
Improved reliability
Version 1.6.0
Adapted to Facebook changes
Now works in theater view and shows up in menus for all posts (as far I as tested it right of course)
Improved popup looks
Version 1.5.4
Adapted to Facebook changes
Version 1.5.3
Corrected post/photo id extraction for file name
Version 1.5.2
Fix comment authors' anonymization
Version 1.5.1
Fix popup hang up when taking screenshot of post without reactions
Version 1.5.0
Anonymous screenshot option
Poll options expanding
Version 1.4.0
Correctly save files as JPG
Improved post id detection (for resulting file name)
Improved appearance on Windows
Minor fixes
Version 1.3.0
Remove "comment as" selector from screenshot
Remove automatically showing theater view from screenshot
All versions on Firefox-addons page