Overflow tanks (btw, we use them), mats, drop sheets, whatever are all great but, the reality is; you are going to spill fuel on the tarmac sooner or later. It can easily spill/ leak when you disconnect the overflow tank. I think what Pete is saying is that we've noticed a problem with diesel at our own club whereby, more guys are running it now and we're seeing damage to the tarmac. If that's not a concern for you or your club than there's no problem is there? It is a concern for us, we don't want to get kicked out of a gorgeous facility.
Rather than jump all over the guy about proposing a ban, thank him for the information ( that we've noticed diesel destroys asphalt) and decide for yourself as a conscientious modeller whether you want to use the stuff or not now that you know what can happen.
If you and your club mates are perfect and only idiots spill fuel, you have no worries, disregard the info.
Mike