I think the best solution is to just hide the checkboxes and only show them when you hover over the topic.
Then it doesn't really matter where they are located, because they don't distract attention.
Moderation: topic move
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Add special indication or don't show current category in tools window for topic movement.
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You can move topic to the same category...
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I'd say it hasn't been moved then.
Should probably not display it's own category though. I'll give you that.
Would be nice if it included a text bar above for those with loads of categories. So type (for example) 'develop' and it displays the developers category.