I just noticed that the Facebook App appears to be fixed. It is now possible to like posts which have not been liked by someone else before, and it is also possible to post comments to postings which have not been commented by someone else.
I don't know when this was fixed exactly, but it now works as a charm.
From my point of view, the Facebook app is now almost as useable as the mobile web interface used to be on my Symbian based phone.
Just wanted to let you know in case you missed this improvement.