If you charged very small transaction fees (for posts, comments, upvotes) and charged higher fees for downvotes, you wouldn't completely eliminate the problems but you'd reduce them significantly as it would now cost something real for abuse.
For example, if an upvote cost 1 karma (putting aside for a moment what that translates to in bitcoin) and a downvote cost 2 karma (but also removed 1 karma from the OP), there would be a large disincentive to brigade. Similarly, if a post cost 2 karma to add and a comment cost 1 karma, spamming would be significantly reduced.
As far as doxxing attempts, every new user could be required to pay a "security deposit" (similar to when you rent an apartment). If you break any of the ToS, you immediately lose your security deposit. To get your security deposit back, you close your account.
Finally, by using small transaction fees (and collecting fees for downvotes, as the operators would get the 3 karma for each downvote), now you have something to reward moderators with.
For example, if an upvote cost 1 karma (putting aside for a moment what that translates to in bitcoin) and a downvote cost 2 karma (but also removed 1 karma from the OP), there would be a large disincentive to brigade. Similarly, if a post cost 2 karma to add and a comment cost 1 karma, spamming would be significantly reduced.
As far as doxxing attempts, every new user could be required to pay a "security deposit" (similar to when you rent an apartment). If you break any of the ToS, you immediately lose your security deposit. To get your security deposit back, you close your account.
Finally, by using small transaction fees (and collecting fees for downvotes, as the operators would get the 3 karma for each downvote), now you have something to reward moderators with.