I use a similar archiving method for a facebook group I belong to for Chinese medicine for a group of practitioners that practice a style of medicine from a particular lineage. A lot of very useful case histories are shared as well as the the opinions from very knowlegable members of the group, making the group an invaluable professional resource. FB's group search function is not as good as it could be and who knows when FB might pull the plug or lose data? My method it to copy and paste the post into a text editor then use 4 or 5 different saved filters to remove "like" dates etc and to format it into something that is easily readable. It takes about a minute. This is then saved as a text file with a relevant title including the date of the original post. The text files are then linked together in catagories using mind map used as a KM system linking the case histories to other diagnostic and theoretical knowledge resources. I do this for a similar reason to you more direct control over the knowledge resource allowing me much more flexibility in the way I organise, view and store the knowledge. I switch on notifications for any post that I copy so that I can update my copy if someone add something interesting to the discussion at a later date.