Will a sharpener for a wider edge ruin a knife with a narrow edge?
If you sharpen it with a 20 degree edge, it will remove material until it matches the 20 degree bevel.

It is up to you whether you like this better or not; however, if you selected this particular knife because you like the way it feels and cuts, the 15 degree bevel may be a contributor to that.

Will it harm the knife?  No, but it will change its performance characteristics.

Sharpening Supplies provides a table of common bevel angles for various purposes, but indicates it is mostly up to personal preference.  They indicate 20 degrees is common for chef's knives, and go on to say:


  The lower the angle the sharper it becomes, but it also becomes less
  durable and more prone to chipping. If you seek a very durable edge, a
  larger angle is preferred because it can withstand more than the
  thinner edge of a low bevel angle.