Looks like a problem with the antialiasing pixels on the letter borders. These pixels are a blend of the text color and the background color. As such they may not be selected by a color select (:colorselect
or a fuzzy select (:fuzzyselect unless you use a very large threshold, but then other problems arise. But may be you can just do a rectangle selection that includes the text you want to move.
However, on the whole you should have your text alone on a transparent layer, with an underlying black background. As long as you keep text and background on distinct layers plenty of problems disappear. You just make sure you don't alter the partial opacity of the border pixels in the text, but this is much easier to do when these are not blended with something else.
or a fuzzy select (:fuzzyselect unless you use a very large threshold, but then other problems arise. But may be you can just do a rectangle selection that includes the text you want to move.However, on the whole you should have your text alone on a transparent layer, with an underlying black background. As long as you keep text and background on distinct layers plenty of problems disappear. You just make sure you don't alter the partial opacity of the border pixels in the text, but this is much easier to do when these are not blended with something else.