This is not accurate based on my testing. If I browse to HN while logged in to my account from the affected network, that account can never post properly again.
Edit to add: Without more details from you, I can imagine the mods being hamstrung with respect to figuring out or explaining what's going with what you're observing. Likewise, there's nothing preventing you from continuing your comments here while also emailing them. Particularly as it seems you'd like to continue to participate on HN. I can imagine you'd prefer to do so without the hassle you're currently experiencing.