Nick,
As Paul says, we do have a lot of private people registering on the site solely in the hope of selling things for a variety of reasons and if we were to permit them all then the Forum would very quickly become a bit of a 'bring and buy stall' which is not what it is meant to be for. There are plenty of alternative sales channels such as Ebay and the like which can be used.
Many regular contributors to the Forum use the 'Latest Posts' facility and we are keen that this should reflect the ongoing model boating discussions and not be clogged up with sales messages.
I will occasionally make an exception if, in my judgement, the situation warrants it but this a fairly rare circumstance.
Regards,
Colin