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Can I remove someone who is watching me?
The ability to remove yourself from someone else's deviantWATCH (or Friends) list is provided through the use of the Block Tool, which may be found in your Edit Settings page under the 'Personal > General' section.
By placing a deviants username on your Block list they will be unable to add your account to their deviantWatch (or Friends) listing and your account will be removed from this listing if it has already been added.
There is no other manner of performing this particular function.
For related information please refer to the FAQ concerning the 'Block' feature.