This is not so much of a programming question as it is about the convention. What does 'Ack' conventionally mean as an alternative to just reply to a comment on a code review in Gerrit?
Does it mean I agree with you but I am not going to change it and/or I have read and disagree with your suggestion?
I realize this is very similar to another question asked by amphibient but not quite the same as that has to do with 'Done':
In Gerrit, replying to a review comment with "ACK" means "I agree with your comment". It's a little different from replying with "DONE" because the second one means "I agree with your comment and I've changed my code accordingly".
These pre-programmed short answers are used to "accelerate" the review process, but if you think they can cause some kind of confusion, it's better to avoid them and let a better answer to the comment.
Important: always answer EVERY comment.