User blog comment:DaNASCAT/Technical Update: February 24, 2015/@comment-23989026-20150225155534

"The font size in the classic editor's pure source mode (i.e. visual mode disabled) is reducing by 0.5px, to become consistent with source mode's font size when visual mode is enabled."

Is it possible that you give advance notice on projects that you are working on? I notice my font had shrunk and being wasting time trying to locate what I did to make it do that!