This problem reproduced not only on minimize of certain floaters from description, but for all expandable textboxes after resizes.
It happened because of hideExpandText() call in LLTextBoxEx::reshape() that broke lineendings.

- Removed it from there so text expands now only when clicking "More" link- it's the only time when it should be shown, and
also doesn't have problem with breaking anything because of calling setTextBase() after it.