Student or Learner
Additional comments in the parentheses are started after a full stop. Shouldn’t they be started with a capital letter? However, they don’t end with a full stop. Is it why they are not considered full sentences, therefore do not require capitalization?
From the Cambridge Dictionaries:
We are holidaying in Northern Ireland next year. (name of a region)
Perth is the capital of Western Australia. (name of a state)
San Diego is my favourite place in southern California. (a part or region of a state but not the name of a state)
The difference between the almost right word and the right word is really a large matter - 'tis the difference between the lightning-bug and the lightning.
Yes, they are not sentences, so they don't don't require capitals or a full stop.