I have thought about this petition, and I won't be signing as it's the behaviour not the format that needs to change. I don't believe there is any real desire for this behavioural change based on available evidence.
David Cameron, 2005:
"And we need to change, and we will change, the way we behave. I'm fed up with the Punch and Judy politics of Westminster, the name calling, backbiting, point scoring, finger pointing." Source
David Cameron, April 2, 2014
"Punch and Judy politics returned to prime minister's questions on Wednesday. David Cameron called Ed Miliband and Ed Balls "Muppets"." Source
David Cameron, April 3 2014, defending "muppet" name-calling:
"I think the language in the House of commons where there's a lot of banter, I don't think that's inappropriate." Source
David Cameron, April 9 2014:
"I’m trying to introduce something new with my children which is a little quiz at breakfast time...I said, “What do we know about Prime Minister’s Questions?” And my 8-year-old son said, “Oh that’s when you shout at each other and call each other idiots and muppets.” And it turned out there had been a feature on Newsround, but he closed this conversation by saying, “I watched the feature on Newsround; I was very proud, daddy,” which I’m not sure was the right answer."
Source
In the full context of the speech above, it is clear Mr Cameron thinks the anecdote is funny rather than showing any need for change.
It's nearly 10 years since he said he wanted to get rid of "Punch & Judy" politics - and this is one of the reasons why people have little faith in politicians, because they say whatever they think we want to hear but it is backed up by very little substance.