When you double-click into a text-field, all text is selected (I find that pretty disturbing), then when clicking to the specific location you want to edit the text, the more-menu appears which opens a submenu for adding the text to other tools that I have installed (Things, Fantastical and more). Please work on the text-field-behaviour.
We are sorry to here you are experiencing issues with XD. If you are having issue in editing any words or letters in a textfield, give it a triple click instead of a double click. On clicking it thrice the cursor points to the clicked position and you can edit anything in between the lines/words.