Hello programmingzeal,

No, it’s not forbidden, and there’s no need to delete a cross-post. It’s simply considered polite to let the monks know that a query is cross-posted, so they don’t waste time addressing a question which has already been answered elsewhere. LanX was just giving other monks a heads-up.

Cheers,

It means cross posting on different forums is forbidden

Not forbidden, just customary to let us know.

When asking for help you don't waste the energy of the helpful.

I personally only switch forums for the same questions after some days of unfruitful waiting and not without linking back for reference to the results already achieved.