Here is one suggestion - but it implies quite a bit of police work from the madmins, and of course a lot of self-policing from the members.
1- Determine which areas are "no fluff allowed", "fluff allowed but keep it low" and "fluff welcome"
2- Post a visible warning somewhere around each area as to which level of fluff will be tolerated.
3- Enforce ruthlessly. Remove fluff posts from "no fluff allowed" zones, and post madmin warnings (in red for example) when the tolerated level of fluff is being reached in a "fluff allowed" zone (with or without a warning that any further fluff will be removed).
*Important* : each temperament's members should be the ones deciding what level of fluff will be accepted in their house. I suspect that, for example, the NFs would welcome fluff, while the NTs might prefer to keep their house a fluff-free zone (and maybe the SPs and SJs would like to go for something in-between?)
Also: posters creating a new thread could be allowed to set the tone for their thread, by asking in the opening post that it be "no fluff please" or "anything goes", no matter what area it happens to be posted in (ie for example a "no fluff please" thread posted in a "fluff accepted" area would still be treated as a "no fluff" thread and any fluff would be automatically removed). This would allow, in that example, posters who don't like fluff but want to ask a question that belongs most properly in a "fluff accepted" zone to post their question while not having to fear their thread getting swamped with fluff beyond their capacity to deal with it.