How to disable "distance doubling" in a sketch?

I do not know of a way to turn off this new feature - but it should only happen when the line you are crossing is a construction line, not a model edge...

If your line is a construction line, it's the same as a centerline.  You're right in that case, if you are on the near side to what you're dimensioning, it is the shorter distance, if you cross over the construction line it doubles thinking it's a revolved centerline dimension.  If you want to place the dim on the opposite side but reference the shorter side, you can 1) place dim on shorter side, then move, or 2) after you've selected your two items, RMB to 'lock' the dim location/orientation, then LMB to place wherever. 

I personally wish SW would differentiate between CL's and construction lines, as it will turn a CL in a sketch to a solid line if you revolve about it (sort of the whole point to dimensioning to a CL in the first place, IMO).

I do not get the "doubling" you describe when dimensioning between an edge and a line.

As Jeremy and Justin said, this does sound like the correct behavior for dimensioning between a construction line and a line.

Dwight