Mark's PDF is still mostly correct. "Effective" mufflers had been added to the rules prior to 2003. 2003 put in a measurable 8mm exhaust size.
But further engine improvements immediately were worked on. By 2008 the exhaust was reduced to 6mm to keep performance in check. A Russian flyer developed a computer scoring system to keep track of scoring, randomly draw the matches, and other details. It GREATLY simplified matching and score tracking, if anything in F2D can be called simple.
Automatic fuel shutoff's were, I believe, mandated in about 2008. So far it is still in effect. If a plane is cut loose or just breaks loose the shutoff has to be obviously slowing the motor before is leaves the flying circle. Most flyers seem to have adopted centrifugal swing arm shutoffs. Unless they are damaged in a collision they will work well enough to satisfy the rule, except when they don't. In that case the judges award the flyer with a loss. This has lead to instances of one flyer purposely manages to cut his opponents lines. Depending on the site it may be impossible for the shutoff to work fast enough since the plane speeds up quite bit with no lines.
The event has been flown pretty much the same since 2008. As a result, the number of contestants has not grown much, if at all. A big contest with 30 entries takes at least 2 full days of dawn to dusk flying. There will always be some 5% of the matches have to be reflown for varying reasons when the judges can't call a winner. But it's still great fun to watch when you see two good pilots fly a nice clean match and don't require any "senate" judgements on who won and if a refly is needed.
If you want to get into it you might want to plan on 6 engines, spare parts, many, many propellors, lots of spare lines(I don't know if the FAI has outlawed Spectra lines. Letting the lines get wrapped in a match the Spectra lines will usually lock of the opponents lines within one loop.) 12-24 planes. Lots of trimming and solo practice to be able to fly the plane everywhere without looking at it all the time.
If you do start flying a lot of F2D planes get 100 sets of good ear plugs. The noise is still a LOT.