I've never had an Admin issue with parts either.. As long as don't "advertise" the parts you have, I don'y think it's a violation..
"Need a 1/48 Tamiya A6M2 Canopy!" for a thread-title, with the post of "As stated, I need the canopy for the 1/48Tamiya A6M2 Zeke. Anyone have a spare?" will work..
Thread title of,
"Spare Parts-I Got What Ya Need"
with a post consisting of a list or link to a site of all the spare parts you have, free or not, is frowned upon and is definately advertising...
Regardless, once someone replies that they have a part you need, finish up the "transaction" back-channel, in PMs (Conversations)..
I don't sell spare or replacement parts, BTW.. I give them away, and only ask that the recipient "pay it forward" to another modeler in need some day..