I meant to emphasise “both gateway and node”, but just to be sure let me rephrase for future readers:
Any hack for a gateway on the TTN community network that only works for specific nodes, is harmful. (Same goes for, e.g, single-channel and dual-channel forwarders, even if those work fine with some non-standard nodes that only use a subset of the channels.)
Also, as covered above: hacks on either gateways and/or nodes on a private network might be harmful for all networks that use the same shared radio spectrum. Same goes for pushing the limits in a private installation, like apparently affects, e.g., Sofia.