There are many issues with the HTMLEditor doing odd things and breaking the formatting in the document.

Here are steps to reproduce two issues that arise in basic editing:

Issue A:
1. Open an HTLMEditor and type "Hello World"
2. Select "World" and increase the font size to 36pt (note size was previously 12pt)
3. drag-select from the "d" in "World" to the "H" in "Hello"
Result: The font size of the whole line snaps to 12pt.

Issue B:
1. clear the content of the HTMLEditor and type "Hello World" again in 12pt font.
2. select "World" and change the background color to green
3. click past the "d" to remove the selection and confirm the background color
4. re-select "World" by double-clicking on it.
5. change the font size to 36 pt
6.click past the "d" to remove the selection.
Result: The background color for "World" is only applied to a 12pt high bounding box. The tops of the letters in "World" are outside of the green background - but the width of the background did expand to include all letters of "World"