RapTarX is correct that the lowest rank has a minimum time limit between two posts is 360 seconds ~ 6 minutes. It was applied per rank before the merit system, but after we had the merit system, it has been applied with activity only (maybe I understand it wrong).
I think is more rank related, the activity now is just a part of the equation and solely gaining activity should not give you any benefits. The post you quoted is from 2013 and many things have actually changed. If you see the OP is says it obsolete now.
The new membergroup limits work like this: (Edit: Obsolete, do not use)
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