I recently submitted a suggested edit to this answer on HP DL380p Fans run 100% as soon as OS Loads but even though it highlights a potential fire risk involved with following the solution given in the answer, the edit was rejected.
Luckily my most recent comment has not yet been deleted (my previous comments were).
The answer suggests using a 1W resistor to slow down fan speeds, but when run at 100% PWM, as in the question, the resistor has to sink over 3W (from the specs and verified on the bench).
I tried out this solution with 2W resistor packs (made of 2x1W resistors) in my server and even though my server doesn't even run the fans at 100% except for at start-up, one of my resistor packs is already started showing signs of overheating. It had burnt through the heat shrink used to protect the leads and part of the outer covering has starting to flake away.
I originally questioned this answer (in comments which have been deleted) because I found a video which showed resistors getting to 150°C when using a similar solution to this, and I asked a question on electronics to make sure my calculations were correct.
If someone follows this advice and isn't careful about making sure the resistors don't touch anything, and where the resistors aren't in a the fan air flow (rather than hidden behind the fans housing, as in the pictures in the answer), this could potentially pose a significant risk of getting hot enough to ignite non fire resistant plastics in the case.
So, given the potential consequences, should I rely on my comment highlighting the risk not getting deleted, or should my edit have been approved?