Not really. Devaluing a single vote insitu once in a while shouldn't be that negative on the system as a whole, especially if there is suspected fraud.
The problem with banning fraudulent users is that they are tenacious, thats's a big factor in their committing fraud in the first place, they are usually on a "mission," see: https://en.wikipedia.org/wiki/Wikipedia:Single-purpose_accou... (not really the same as a fraudster, but this is a common archetype)
They will just make another account or increase their efforts, better to keep them in their container within the system.
The problem with banning fraudulent users is that they are tenacious, thats's a big factor in their committing fraud in the first place, they are usually on a "mission," see: https://en.wikipedia.org/wiki/Wikipedia:Single-purpose_accou... (not really the same as a fraudster, but this is a common archetype)
They will just make another account or increase their efforts, better to keep them in their container within the system.