I believe the report in August 2016 was about the time of the preliminary.0a4 release, months before the final 3.6.0 release.  Something could have easily changed after.

I should have been more detailed and accurate is what I wrote.  In paragraph 2, I said I observed the color bug with ' or '''.  In paragraph 4, I said that the color bug depended on the number rather than type of quote.  The later was accurate.

My C: directory contains a Logs directory.  If in 3.5.4, I type '/, the / is green and the selction box appears.  When I type L, the L is green and the selection moves to Logs.  When I type o, the o is white (I am using IDLEDark).  Or if I backspace and type L, the L is white.  Or if I move with the cursor, the inserted word is white.

This is not true in 3.6.5.  The color bug seems fixed.  The autocompletion window, which handles interaction when the window is open, was patched in #24570 for a Mac-specific bug.

The completion bug remains in 3.6.5 and newer.  If I type '/L' or '''/L''', L is not completed to Logs and the box does not disappear. The opposite is true for " and """.  "/L" completes to "/Logs" and the box goes away.  Also, "/L/ completes to "/Logs/, leaving the box open for selection of a subdirectory.  "// does not complete to the first item in the box -- at least one action is needed.

The effect of // is analogous to .. in attribute completion.  []. brings up the box.  A second . completes the selected name and brings up a new box with subattributes.  This does not require an inbetween action.

Cheryl, is this clear enough to reproduce?  It is possible that Linux does not have the bug.  It should be in autocomplete_w.py and we already know that this has system-specific behavior.

I would be reluctant do anything beyond trivial without improving the autocomplete tests.  I added #30348 and #30666 as dependencies, at least for the present. This issue is a dependency master autocompletion issue #27609.