I'll try and explain the system a bit?.

The incoming BT line has only two wires, they connect to pins 2 and 5 of the six pin socket used.

The BT master socket is the only one that contains any components, these are a 1.8uF capacitor between pins 2 and 3, a surge suppression component across the incoming line (pins 2 and 5), and (optionally) a 470 Kohm resistor between pins 3 and 5.

The sockets in the house are all connected together in parallel by three wires, on pins 2, 3, and 5 - although 4 or 6 core cable is usually used, the others don't normally do anything.

The 'bells' in the phones connect between pins 3 and 5, so the 'bells' are all connected in parallel as well, but all fed through the single 1.8uF capacitor in the master socket. This capacitor can only supply a certain amount of power to the 'bells', so once you get two many 'bells' connected to it then some may stop ringing, as there's not enough power for them. The amount of power each phone ringer requires is called the 'Ringer Equivilance Number' or REN.

I've never taken a micro-filter to pieces, but I see no reason why it would have any connection at all to other than pins 2 and 5 (except pin 3 will loop through on the phone side only), so REM shouldn't have any effect on ADSL?.