When you select a word or phrase and copy/move it to another sentence, it breaks the word spacing in both places.
The word in the destination ends up with no space character between words.
If moving the text, it also leaves two adjacent spaces between words at the origin.
Similarly, if you select a word and delete it, you’re left with two adjacent spaces instead of one.
The standard for most applications (browsers, text editors, etc) is to remove the extra space left behind and/or insert a space between words at the destination, so I think this is a problem.