Among the moderators there is no distinction between removal of the DPF, catalytic converter or EGR. All are illegal and will be dealt with accordingly.
Not to be picky: it is NOT illegal to remove DPF, cat, EGR or ANY OTHER modifications you want to do to your car. You can do whatever you want to the property you own.
Technically, it is only illegal to drive such modified car on public roads.
All of us who have modified their cars are CERTAINLY only using them off road, for racing, etc.
But so is driving over the speed limit (yet a few cars a sold in the US with top speeds exceeding the speed limit; not illegal, just not legal to USE that top speed on public roads).
BUT: rules are rules. And if the owners/moderators of a website stipulate it is not permitted to discuss certain modifications (ditto Uwe over on Rosstech/VAGcom/VCDS for example), then those are the rules.
Just don't scare members or misuse the term 'illegal'.
It is like saying: "guns are illegal" or "the use of guns is illegal". Nope. Just killing people with them is illegal.