Comment 2 for bug 172097

It's clear that this is the intended behavior and it's not a bug, but I agree with the reporter.
From the user perspective, the way the blur amount is measured is quite hard to understand/predict. Re-using styles (for instance, a drop shadow) is a very common practice when designing, and not being able to repeat a style because it will change according to what object is applied to, is very frustrating. The current implementation is quite unpredictable (even using the paste style command).
The button for the blur scaling sounds good. It would really make sense to treat a blur pretty much like the strokes are managed (fixed size, and a switch to allow/prevent scaling).
The problem is how to do that without breaking the SVG compatibility and getting a document with hundreds of style definitions.
IMO, this is something that confuses users and should be solved in some way. But it doesn't seem an easy one.