Secondly, the damage done was accordingly limited: If people saw the delay as questionable, people were given an opportunity to directly punish the government in an election rather than doing so indirectly via Parliament. If there was time to hold a general election with suitable margin ahead of October 31st, then this proroguing would not have been an issue, as we'd be going into an election instead.
> Again, Johnson is not denying Parliament the opportunity to vote on the deal.
It is not up to Johnson or the courts to decide what Parliament may or may not consider critical to do in the run-up to such a major constitutional change. His government serves with the consent of parliament; parliament is sovereign, not the government.
> It is important to really think through the logic here: if Johnson wanted to stop Parliament he would delayed until AFTER October 31. He didn't do this.
This does not follow. If he had announced he would prorogue until after October 31, then he would have to give up any pretense that he is negotiating a deal, because parliament would be unable to vote for it. It would instantly ensure a majority for removing him, as everyone opposed to no deal would have no other choice. His only option if his goal was to stop Parliament was to limit their ability to function as much as possible but still little enough to not push people into deciding removing him instantly was absolutely essential.
I don't think the logic leads to this conclusion. His calculus may have been that the prorogation would be more likely to be successfully challenged if it _clearly_ cut parliament out of the process altogether. By leaving some time for them to sit ahead of his October 31st deadline he likely hoped that the prorogation would stand, he could negotiate a deal, downplay the possiblity of an extension, and then force a vote to approve the deal as the only alternative to a no-deal Brexit given the short timeline.
That would've made the motivations too explicit. He'd presumably hoped to skate by with your argument - "oh, I left a week or two to tackle this minor issue". It didn't work.
In 1997, the justification was to stop a politically damaging report being published before an election.
Again, Johnson is not denying Parliament the opportunity to vote on the deal. Nothing will happen now that Parliament is sitting again. The negotiation will still happen at the European Council meeting at the end of the month, and Parliament will still get a vote on it.
It is important to really think through the logic here: if Johnson wanted to stop Parliament he would delayed until AFTER October 31. He didn't do this.