I actually wouldn't use a blind stitch for this. A kilt hem is typically done with a different stitch that boils down to a catch stitch. It's 6:30 in the morning and I'm in Roanoke Airport and I'm a bit brain dead and I'm drawing a complete blank on the name of the stitch. Anyhow, I'll post a pic when I get home. The stitch that I can't remember the name of produces a hem with a little more "give" and a little less tendency to make a ridge at the bottom of the kilt.

And I definitely would hem the kilt, if only to keep the bottom edge from getting worse and raveling until you can't do anything successful to fix it.

Sorry my brain is mush this morning! Coffee isn't helping.....