[tag:bug] [tag:status-review]

In the current editor using nested `<sub></sub>` html is supported, and can achieve an extra small fontsize. For example: `<sub><sub> Extra Small </sub></sub>`


When writing this in the Markdown version of the RT editor, and then switching over to RT the first `<sub>` gets trimmed, the last `</sub>` doesn't: ` <sub>Extra Small</sub> </sub>
`

Either nested `<sub>` statements should be supported, or the last closing argument should also be trimmed.