The question asked yesterday was similar, not the same.
At the very least mine had two parts, the wording of the link and the check box. The link wording is an easy fix. In the source replace the line "<a href="/index.php?title=XXXX-XX&action=editfamily&w=spouse" target="_blank" title="Add a spouse">add</a>" with "<a href="/index.php?title=XXXX-XX&action=editfamily&w=spouse" target="_blank" title="Add or remove a spouse">add/remove spouse</a>". (XXX-XX is the id if the profile you're on, which is filled in by the script that generates the HTML).
The checkbox is not as trivial, but the functionality users are looking for is probably implementable. First off (which might be causing some confusion), a check box is the wrong widget to use for spouse. A button would implement the behavior the users are looking for and function with the underlying implementation without explicitly and unnecessarily exposing that underlying implementation. Most of the code is already there. I'm guessing the implementation is that the "no spouse" button on the add spouse page attaches a pseudospouse that indicates "no spouse" to the profile. Here's how you could do it:
The spouses line for a profile without a spouse would have the add/remove link and a button reading "no spouse?" If the user pushes the button, the no-spouse pseudospouse would be attached to the profile, just like the user had gone through the current add spouse-press no spouse procedure. That's really the only change needed. If I have the implementation wrong, the basic idea of a button on the profile page doing whatever the add spouse-press button sequence does stands.
I'm not trying to step on any toes. I'm endlessly impressed by WikiTree as a web site, and I would not be surprised by or unsympathetic to the opinion that this is a low priority issue. It is (as you point out) a common user request. From an accessibility viewpoint, the changes I've outlined would simplify things for users with various cognitive disabilities.