While we're on the subject, some other tips/tricks on the spot healing brush:
It behaves differently if you "scrub" with the brush instead of doing a single click. Takes some experimenting to see the difference, but scrubbing seems to change where the brush goes to find its fill. Scrubbing means left-click, hold, and move the brush around a little.
Right click and change the "roundness" of the brush. Make it a long, narrow oval when trying to heal near an edge. Change the angle to match the edge, and it won't "bleed" the edge pixels.