Some "problems with control characters" are not exclusive to CC, but also apply to markup

[lkemmel]

"5.2.4 Problems with control characters" says:

"2. It is sometimes necessary to choose which [CC] to use based on context or the type of the data, and this means that a content author typically needs to select the control codes – specifying control codes in this way for all paragraphs is time-consuming and error-prone."

• and

"Don't expect users to add control codes at the start and end of every paragraph. That's far too much work"

Same holds true for markup, at least in the following cases:

• there is a need to denote an embedding direction (and hence it's necessary to choose which direction value to specify within markup for each inline segment)
• first-strong doesn't represent the content adequately (and hence it's necessary to choose explicit "prevailing" direction within the markup for each paragraph)
• the prevailing base direction is not uniform and thus can't be denoted for units containing multiple paragraphs (but for each paragraph individually)

[aphillips]

Note: The actual section in the current document is 3.2.4

Many of these issues are less true of markup than controls, since HTML5 includes bidi isolation, dir inheritance, etc. However, the cases cited are potential issues for markup. I'm contemplating adding a new subsection for "problems with markup".