Rules could be something like 20 charges on a single post - user gets warned and asked to modify/delete the post, while at 30 post is auto deleted and user gets 2-3 days ban from that particular subboard, 120 total charges on all your posts across the forum in last 7 days - you get banned for 1 week....
It has already been thought over, and not implemented because such a thing can be used negatively by the spammers as well. Now you can't only let genuine users use this feature. So, what if a spammer teams up with some other spammers and plans to get me banned for a week, because I have done something that harmed him, by charging one of my posts? How would you counter such problems?
For a guaranteed week ban the spammer would need to get >100 accounts to make it happen. Due to the fact that moderators would get much more free time after such change, they can spend this time on genuine users appealing such cases of abuse. 100+ users downvoting a decent post could be either a botnet/multiaccounting or a well organized spammers group violating the rules\ideas of this forum. It's good for the forum and its users to detect and get rid of such things, so if anybody tries to do this to you, you simply appeal to the moderators. Moderators can always investigate the case. Punishment for premeditated abuse of such feature and the number of accounts at risk in a collusion case should prevent any attempt of abuse. If the user or group is risking a ban on 100+ accounts just to ban you for 1 week - it's heavily unfavorable to even try.
Other option is doing it a "+/-" kind of stat, where decent users can upvote your posts in this type of scenario, but that would be much more abusable actually.
I, personally, don't think it has been thought over, since shitposts everywhere are still a major problem. The reputation system of some kind is used in most decent boards nowadays, it is proven to be more efficient for huge boards.