Maybe we don't share the same definition of "support". Yes, it is included since a while in OpenACS, but is it supported? If something is default, it should work out of the box and it should be documented how to use it (check the issues above). If people vote for making it default, they either don't care or they don't know about these issues. I would not have brought up maintenance, if there would have been any posting that someone address these.
Just another example, where this impression comes from: the default browser should work with ie8. I tried to figure out, what version of tinymce is in the 5-5 branch. Your posting in the release notes of OpenACS 5.5a1 says 3.1.1, the changelog in the version in the oacs-5-5 branch says 2.13, the .js source file there says 3.2.2.3, while the currently released version is 3.2.4.1 (a few weeks old, why we do not use this one?). Now, try to figure out, whether IE8 works with the included version.
Anyhow, i have spent already too much time on these issues. These are not part of the tip, but necessary to make the decision.