In my review of Howard Shelley's first volume of the complete Mendelssohn piano music (April 2013) I quoted Sir George Grove as saying that Mendelssohn 'never himself interpolated a ritardando, or suffered it in anyone else.' For whatever reason, there are fewer of these interpolations in this fourth volume, but still rather too many for my taste—and, it would seem, for Mendelssohn's. I quite see that fugues on the piano present a particular problem: whereas on the orchestra or in a choir, a change of instrumental or vocal colour can delineate a fugal subject without rhythmic interference, on the monochrome piano 'bringing out' the subject by simply playing it louder than its surroundings can be a crude approach. It's all a question of degree, and here I found Shelley's rhythmic signalling at times a touch intrusive. But only over the 'Funeral March' in Op 62 do I really object—surely any rubato here poses serious risks to the coffin?
On the positive side, Shelley's technique is superb, and anything marked Presto or thereabouts is delivered with tremendous élan. There are also whole pieces, such as the delightful A major Lied, written on the composer's honeymoon, where the music is allowed to flow unimpeded, showing that it can be done.