Just FYI, with #4392 the code-branch of this function is no longer needed at all. (The way it is implemented right now is actually also incompatible with the reworked Code mobject.)

Thanks for the info, Benjamin! I didn't even realize that Code no longer has a code attribute.

With this new information, @henrikmidtiby:

• since the Code branch does not apply anymore, because the invisible Dots would already be removed in the code with #4392, and
• the Text branch does not make much sense (doing mobject = mobject[:] only transforms the Text into a VGroup, but the submobjects are the same and it does not affect the subsequent code),

I would say that remove_invisible_chars() should not really have any of those branches. In that case, it would only do the logic we wanted to move into exclude_dots_from_mobject(). We might as well delete the latter function and move all of its logic back into remove_invisible_chars():

def remove_invisible_chars(mobject: SVGMobject) -> VGroup:
    mobject_without_dots = VGroup()
    if isinstance(mobject[0], VGroup):
        for submob in mobject:
            mobject_without_dots.add(VGroup(k for k in submob if not isinstance(k, Dot)))
    else:
        mobject_without_dots.add(*(k for k in mobject if not isinstance(k, Dot)))
    return mobject_without_dots