When a word is added to dictionary, its capitalized version is deemed as incorrect by the spellchecker. However, the world could appear at the beginning of a sentence, therefore be correctly capitalized.
Available workaround (if any):
Add non-capitalized and capitalized version of new words to dictionary or ignore false mistakes.
When adding new words to dictionary, users can choose to enable the "Case sensitive" option.
This feature would avoid false mistakes highlighted by the spellchecker.