So I am mostly familiar in html and it's easy for me to add non breaking spaces and no space joiner in html but some landingpages will be created by editors without this knowledge. I tried and explayned the great Special Character Properties with adding a non breaking space between words that should not break (for example on mobile phones) and for some combined Words in our Company Language we do need the no break Joiner. But these Spaces just won't work and appear afterwards.
I haven't ever used the special characters menu you're pointing out here, but maybe they just aren't translated into the code properly. Would you mind posting the HTML that shows up in the HTML editor after you add these characters to your text in the Rich Text Editor? You should be able to see the HTML by clicking the HTML button on the toolbar. Then to post that in the community thread, you'll want to use the "..." button in the toolbar here and click the "</>" insert/edit code button to paste it into the post.
It might be that these aren't getting added as the entity (non-breaking space) in the code-view?