Gerben's sequence is perfect. For me, opener's second round 2♠ would be just a "mark time" bid, could have substantial extra strength but nothing more descriptive to say. I don't raise pard's 2♦ unless I have four of them. AP
Another way to address this is within Chat - have table options "prohibit chat from enemies" and/or "allow chat only from friends". (this may well be encompassed by hrothgar's suggestion...)
I'll leave the learned discussion to others. This is an area where I want to have an agreement, and I don't much care what it is, so long as pard and I are on the same page. AP
are we looking at the same hand? This is a game force opposite a standard opening bid. So start with 4th suit forcing [you should have an agreement with your partner for this sequence - is 1♠ or 2♠ 4sf?] then pard can declare 3NT. and likely go down. So perhaps you didn't lose anything playing in 2♥ after all. AP
Assuming responder's 2♦ and 2♥ show 5-card suits, 2♣ promises only two. This makes it ACBL-alertable. Note: if it promises 3 it is not ACBL-alertable. AP references: Natural calls are not alertable unless specifically noted - http://www.acbl.org/play/alertchart.html A minor suit bid is natural if it promises 3 cards - http://www.acbl.org/play/alert.html
Maybe it is time for an Australian-style tournament - 3 days swiss qualifying, then 2 days KO's for the women's and mini events, 4 days KO for the main event. And thanks to BBO - lets us see how tournaments are run round the world. AP
Pard had no idea that you have 5 clubs and declarer has the stiff Q. The 8 should be a normal attitude signal, "please continue clubs". So he has no interest in a switch to hearts. I agree with the switch to diamonds. AP
The first is takeout. The second depends on system. After your strong NT, I thought it was "standard" that the double is penalty in this seat, while if the bidder is sitting over you it is takeout. If it is a weak NT, I would expect takout regardless of the position of the overcaller. AP