After a long back and forth discussion about the pros and cons, while we do want to force IC communication, there is no way to do so. For a long time as everyone knows throughout hl2rp, everyone... and I mean a fuck ton of people in hl2rp use OOC comms on a daily basis. They have no care for rules when it comes to using them since staff can barely ever find out without spending 10 years searching 100000 pages of logs. An over-exaggeration but not something we are interested in doing.
Thus we have made the decision to allow OOC comms to both sides. Rebels, OTA, Vorts, CPs, etc... can now all freely use OOC comms. Of course, metagame is still banned, but you may now communicate via OOC channels while playing, given that you don't start handing out IC information like free candy in them to bait people into metagaming. Those 2 rules still apply.
This means that a few public "Radio" channels will be created in Discord for players to use to communicate. CP comms will become public so you can see when they are in VC chatting together or not. So both sides will know when they are chatting or not.
This was quite a tough decision on our side, but the reason we don't just ban OOC comms is that even if we do, people will do it in secret anyway and there will be no way for staff to tell if someone is doing such or not. That is all.
TL;DR: So when it comes to TBC/S2K, you are now allowed to have OOC comms.