This is exactly the author’s point. Even though it’s implied rather than stated, the premises establish that it’s wrong not to vote. In other words, people should vote (or “not neglect to vote”).

The argument does not support drawing an exact equivalence between dishonesty and not voting. Dishonesty is an analogy used to support the rule about when relatively low-impact actions can still be wrong. All we know is that single similarity with not voting.

The author never talks about imitation. The principle in the argument is that individual actions can be wrong depending on the possible consequences if everyone did the same. It’s hypothetical, not a claim that everyone will do the same.

This is not stated in the argument. The author is only talking about individual acts that don’t make much difference on their own.

This claim about dishonesty is only used as an analogy to support the author’s rule about when low-impact actions might still be wrong. This supports other parts of the argument, and is not supported itself, making it a premise.