Steps to reproduce:

1. From View > Columns, hide all but (for example) Title and Username
2. Try to scale Title column smaller by dragging the separator between it and the Username column to the left.

What happens:
A new, blank column appears between the two columns and grows bigger as I try to make Title column smaller.

What I expect to happen.
For Title column to get smaller, Username column to expand into the space being freed.

Further info:
This is on up-to-date Quantal, up-to-date Precise is also affected.