In the last version I simply negated the evaluation output if Mediocre was playing black. This way a 'positive' score would be reported as negative, meaning black was ahead, instead of positive (engine is ahead).
While this seem more logical to me, unfortunately the protocols does not work this way. The evaluation should always be in terms of the engine, and not on what side is ahead.
Fortunately the thinking output does not affect the actual thinking of the engine, BUT some interfaces (like Arena) adjudicate games based on the evaluation of the engines. This can lead to Arena adjudicating a game since it thinks Mediocre considers its position very bad, while in fact it considers it very good.
I will change it back in the next version.