That may very well be, but I'm generally surprised
to see that a testnet "reset" has so many dependencies
left on the old chain.
Would it be possible to have bitcoin-qt refuse
all testnet packets from a peer that identifies
as being below a certain version ?
Yes... but having peers with a completely different block chain from you connect is a good way to shake out obscure bugs. Like Bitcoin-Qt's "how many blocks are in the valid chain" code getting fooled...to see that a testnet "reset" has so many dependencies
left on the old chain.
Would it be possible to have bitcoin-qt refuse
all testnet packets from a peer that identifies
as being below a certain version ?