That's a bit of a misrepresentation, and I'm posting in an effort to clear up any misunderstandings for anyone viewing this thread.
Once you block someone, they essentially no longer exist for you. Let that person stop taking up your mental real estate. Forget they exist. They're essentially gone. The idea is that it gives you a break from someone who is negatively affecting you and/or your mental health. Blocking a user isn't intended to be any sort of punishment for the user in question (staff handles disciplinary actions, not random people on the site). Blocking them keeps them from being a problem for you anymore. Obviously, if you are concerning yourself with everything they may still be posting or continuing to worry that they exist, you are not allowing the blocking system to do its job and misunderstanding the purpose of the block.
Harassment is reportable, obviously, and punishable. People don't just get away with inappropriate behavior on the site. We handle it. And if someone is behaving terribly, but you have them blocked, it's not something you need to worry about; staff will handle it. Staff will see it and deal with it, if it needs dealt with. If staff somehow manages to miss it, it's common for other site members to report particularly egregious behavior. You may not see it, but as someone who works in the Ticket Center full-time, I can tell you that when things get out of hand, we get a lot of reports about it (and we appreciate that people are keeping an eye out). It's not your job to singlehandedly police the behavior of someone you don't like, and not something that you need to worry about. :)
If someone attempts to evade the block, that's obviously problematic, so let us know if you have someone blocked and they've evaded that block, and we'll deal with it. Commenting on a post that you happen to have posted, or commenting on a post that you have posted in, or expressing an opinion that is different from your own is not necessary harassment, or block evasion. You'll know if someone attempts to evade the block because they will have contacted you through some means, or had someone else contact you on their behalf, etc.
Ultimately, I think there's a bit of a misunderstanding here of what constitutes harassment vs. a personal disagreement, and what the block system is for. I hope this clarifies a bit. :)
Since this matter was discussed and handled in the ticket and further clarified here, I'm going to go ahead and lock up the thread before things get too derailed. As always, if there are any points of confusion regarding a rule, the best place to ask is in the Ticket Center so that you can get an official staff response.
I hope everyone has a great week!