Resolved
Reported for: Toolset Layouts 1.8.10
Resolved in: Toolset Layouts 1.9
When adding invalid HTML structure into a Visual Editor cell and trying to save the cell, it strips the invalid HTML tags and removes them completely.
The problem will be fixed in the next version of Layouts.
In the meantime, the fix can be applied using this patch. Download the patch, extract its contents and replace:
utils.js
file in layouts/toolset/toolset-common/utility/
folder.