Documentation has fallen behind a bit. There appear now to be five levels of HTML:
1) "Default permissions" - has a list of about 20 HTML tags, most of which appear to match up to the minimal installation of the TMC Editor. Use of the HTML editor to place HTML tags while writing a new post generates the "Invalid HTML" error trap, and the tags are typically turned into text equivalents (e.g., ">"). However, writing a post in the RTE, then opening it in the HTML editor, allows manipulation of default HTML tags. This behavior is sometimes hard to predict.
2) "Simple HTML" - adds the IMG tag with attributes. We set this permission to "Deny" for basic users, given that our community began almost exclusively as a support community for end-users. I have wondered if the unpredictable behavior around the default tag set has anything to do with this setting.
4) "Advanced HTML" - thanks to CarolineS for the reminder. How is this different from the "embed third party content" version?
5) "Full HTML" - Trying to figure out how this is different from the previous two items. Since it isn't documented in https://community.lithium.com/t5/Roles-and-permissions/Allowed-HTML-Tags/ta-p/57476, it's not obvious what is the difference.
So the major question is, Why is 3 defaulted to "Grant", while 4 is defaulted to "Deny"?
A corollary question is, Why does the HTML editor even appear on discussion boards, when use of Simple HTML is denied for forums?
Don't forget "Advanced HTML" as well, which I think would be yet another category of HTML - see https://community.lithium.com/t5/Support-Forum/Simple-vs-Advanced-HTML-for-posts-amp-signatures/m-p/... for details on what that is.
Thanks, you're right. We really need a matrix that defines each term, not just in terms of exactly which tags are involved, but also the interactions between variations at various nodes.