If I double-click on a word, and then extend the highlight to include a trailing space, the space is not persistent during copy.
Example: This is a sentence.
Highlight "This" in the example. Extend the highlight to include the space. Ctrl+C.
Insert cursor immediately after "This". Ctrl+V.
There's still only one space after "ThisThis"
Now insert cursor anywhere within "sentence". Ctrl+V. No space is inserted after "This".
In both of the copy operations, the trailing space has been dropped.
Note that I don't support the M$ method of ADDING an unwanted space after double-clicking. The simple rule should be "What-you-DO-is-what-you-get". So, IMHO, the CN result after double-clicking a word is CORRECT. (And the method used by this forum software is INCORRECT.
