Some basic thoughts:
The problem is:
When I want to replace this word with another word in this second case, auto-completion won't pop up.
Wouldn't it make sense to exclude the trailing space when marking a word with the keyboard (and align the behavior with the mouse behavior)? This would enable auto-completion from the very first sentence, without entangling your fingers (= mark a word and go one space back to the left). What disadvantages would a change of the current behavior have?
Just as a side note: TextWrangler and Bluefish behave like in Case 1, Word for Mac and LibreOffice like in Case 2.
The header should read "words with", not "wordsmith", of course.
Torsten: The header should read "words with", not "wordsmith", of course.
I hope this is not the result of using the Dictation.app, there are quite a few mistakes (award, String key) in the message that point in that direction.
I think you could write a script for the shortcut for CafeTran only to get rid of that trailing space, but wouldn't "typ first, delete later" be a lot easier? I don't know, I'm a mouse.