If entities/tags are used in a TextArea then it uses the full string length for caret, etc, not the string's display length, which is a pain to workaround.
e.g. in a string "hello", arrow keys will move caret from 0..5. In "&pig;" it also goes from 0..5 but should be 0..1
EDIT: jlnr suggests just not supporting entities/tags in textinputs.
Superseded by #304. Pseudo-HTML markup should be an opt-in feature, and it should not be used when implementing text fields.