What is magical about a 45 degree bank?

At 17:48 05 October 2013, son_of_flubber wrote:
I know that a 45 degree bank is useful for flying small circles and
staying
in small thermals, but is there something special about a 45 degree bank
compared to say a 50 degree bank?

For example, does the designer intend for the glider to do something
special at 45 degrees? Is the glider designed to balance aerodynamic
forces in a particular harmony at a precise 45 degree bank?

The only thing I am aware of in relation to 45 deg of bank, is that it
gives the minimum height loss in a 360 deg turn. This is not of much help
in turns in thermals.
Dave