The problem was originally. Specially put unchanged version and checked.
But this problem also pops up on other texts.
This one was given as an example. But what that passes.
If you use htmlSpecialChars, then it naturally stops transcoding the html code and then displays all the text with the formatting tags.
Maybe it works correctly, but in other modules this text skips and saves.

Or refuse to use the apostrophes...
Which is not entirely correct. IMHO

It will be probably the best to replace the backend.
Take a look at this: https://github.com/mambax7/lexikon/tree/feature/backend_test

The two tabs of interest to you are on the right hand-side, Categories and Entries.

With these, you should be able to save the apostrophes.

Please test it and see if it works for you. This is really a "quick & dirty" branch, so don't use it on a production site - this is only for testing as a proof of concept.

Yes, it works in these tabs.
How much do I understand that the challenges change completely?
Pretty interesting. The truth is not yet understood more tightly, but I saw a very interesting version of the localization of search and sorting.

We need to move to XMF and start utilize all the cool features there, that will make our lives much easier.

Unfortunately in the past, because we had no clear standards, and because XOOPS is so powerful that you can do almost anything in any way you want, we've ended up with a lot of different modules, developed in many different ways.

So now we have to bring all of them together, and standardize by selecting the best ideas and implementing them across all modules. This will improve also the security of the modules, as we'll be re-using code that has been already tested.

I wish, the process would go faster, but at least we have pretty much all modules now using the same Admin GUI, and we're moving more to leverage XMF on the back end.

As you've seen here with Lexikon, the goal is to be able to "swap" the basic CRUD operations, and start consistently using XMF, Criteria, and XoopsPersistableObjectHandlers.

It's a lot of work, but it should be faster than rewriting the backend for each module.

I think it's necessary to create a topic and publish recommendations on the development and updating of modules. And also to draw up an approximate list of modules that users use and gradually bring them to standards ...