Clients used to be able to edit a free text HTML row in Page Builder v3. This was switched off for everyone as a security measure. Some sites had already built a number of pages relying on this row (partly because some of the newer formatting tools like the WYSIWYG editor and margin controls weren't turned on for them), so removing it broke their ability to edit those pages. The plan now is to bring editing access back, but backed by proper validation instead of a blanket switch off.
