I've noticed lately (for example, in all versions I compiled between April and today) that some effects come up twice in the lists under different names, for example

Face blur == FaceBl0r
Edge glow == Edgeglow
Denoiser == hqdn3d
Threshold == Threshold0r
Sharpen == Sharpness
etc.


Also, I think that some effects that are currently under "misc" would be easier to find, if listed under an more specific category, for example

Audio wave => Audio
Bezier curves => Color (or Color correction)
Denoiser => Enhancement
Mask0Mate => Alpha manipulation
Rotate and shear => Distort
Rotoscope => Alpha manipulation
Sharpen => Enhancement
etc.

Looks like there is something broken with your effect list.
I don't have any duplicates and most effects are in the proper folder (in r5715 jbm moved some more 3 effects from the misc folder).
Make sure you update to the latest revision since some recent changes in MLT forced us to update the effect loading.
If the problems persists have a look at your kdenliveeffectscategory.rc

The local kdenliveeffectscategory.rc was OK, but there were some leftovers from and old installation in /usr. Deleted these, problem solved.