Also it's good to keep in mind that some of the older members of PMC have deleted a big number of their submissions online, which causes their level to decrease.

I agree with you partially on this. While you should check the level and the date they joined, I think the acceptance level should be around 10 and up. The date thing is kind of hard to judge by, too, because some people can get to level 5 instantly in a week by writing a good blog or making a great map. Still a nice blog though :)