Hey @HAWK , et al.! Good discussion here!
My 2 cents (more questions than answers : )
I think best practices are always a good starting point, but best practices are a by nature a lowest common denominator. It takes the totality of the web and all of its varied users/ demographics/ states/ experiences/ strategies/ goals and distills it down into a black/white, yes/no answer that isn't always the "best" solution for all instances.
If possible, the decision should be made from the standpoint of influencing the specific experience you are looking to improve. What is the experience level of the average user in this case? More advanced users/digital professionals are probably already creating their own click experiences (eg. Steve Crow's comment).
So, would changing link target from self to blank help this audience achieve their goals or enhance the experience? Would it support the goals of the organization (eg. increase/improve engagement?) What about differentiating link function based on what the link does (like Jacqui Dow's approach) or @jaisonjustus's suggestion echoed by Irreferential... Even though both might be a new pattern to learn for some, could it benefit a majority of users (again based on audience, demo, etc.) experience?
It is always a good idea to start with "the rules", but I also think rules are made to be broken... if there is a valid (hopefully measurable) reason and it makes sense to do so from a business, user, experience standpoint.
(sorry I couldn't use everyone's @ link... new users can only link to 2 ppl in a reply!