Criticism:
The aesthetic value of tags is somewhat... bad. Also, it will force people to submit card ideas with a new, more difficult format. It will result in arguments as to "what tags should this have" and more work for Curators. I'd personally prefer a more subtle change, such as the tag line addition in the table along with Hyroen's code to generate very specific searches while still being very readable and having a normal title. I'm not sure as to what to do for the possible discussions and the Curator work. Maybe keep it as a simple add-on to card ideas, completely voluntary?
Furthermore, the purpose of this project is to limit the similar card concepts. This is all good and well, but the problem is not (or rather not just) the inability to search the boards for similar concepts, it's the fact that nobody does. To hinder the popular concepts from being introduced in the polls, you should have a filter to card ideas. But how would you rule a card concept that has been repeatedly in the polls in the past but is now in the Archives? Or a card that is near-identical to another, but in a different element, with a different flavor, is part of a serie, or any other number of possibilities? Also, the popular vote has insofar been acting as the "filter" I am talking about. Are we going to introduce a sort of jury (be it Curators or anyone else, it will still be a sort of jury) to judge the ideas preemptively and decide whether or not they are different enough? Are we going to count on simple suggestions and gentle reminders to card creators? If this is the case, what difference is there between having the tags and not having them? The card owner will see the card eventually and comment on it (which is what is happening now).
I'm skeptical of the actual utility of this project. Can you convince me of its effectiveness?