Sharing an article to Facebook with Opera (version 46) causes the article to be classed as Spam by Facebook. The article is then deleted from my timeline. Some experimentation reveals that the problem is most likely Facebook's response to the Opera download link that is automatically inserted in the post, "Found with http://opr.as/operabrowser" . Facebook responds to a post containing the download link with, "We block content that looks like SPAM according to our community guidelines." This post will be automatically deleted in 30 days, or you can delete it now."
The work around is simple. Just delete the download link before you post. I've use Opera for some time now without encountering this problem. It appears that Facebook has tightened their criteria for classifying posts as SPAM.