More than anything, I really think it comes down to whether or not its typically acceptable to tag owners of multiple accounts with negative trust, just because they own multiple accounts. Second comes whether or not trading/selling merit is generally acceptable, and to what extents.
The general consensus between the remaining active DT members that do attempt to *improve* the forum (not the DT members that are active and don't really do anything in that regard) is yes. It was explained properly over here:
untrustworthy behavior = negative tag
asking for/buying trust/reputation = untrustworthy behavior
buying accounts = trying to buy reputation
begging for merit = trying to ask for reputation
These correspondences should be accepted by all members... but unfortunately, some do not view it this way (typically account traders).
Non malicious false positives are going to occur in pretty much every system. As long as the rate is very low, it is fine.