I love this song. It is a short breather between epics on SEbtP. It offers a mood change from the previous song and is part of the concept of the album (this particular song representing deception).
In the early days, the band wrote songs like this to serve as breaks in their records (which I think makes the albums more diverse and therefor more progressive.....it's always nice to have a short love song amidst 10-minute "epics"). Between songs, Peter usually had to change costumes at the live shows, so Phil and the others would handle vocals on one of these short songs while Peter changed (More Fool Me, For Absent Friends, Harlequin). So there is actually a legitimate purpose to these songs.
I think that it is snobby when reviewers take points off rating of this album only because of More Fool Me and I Know What I Like. They are not simply 'poppy' commercial songs, but crucial parts of the record as a whole.