[mooreds]

A few options.

* Keep in touch with past colleagues. Use linkedin. Congratulate them when they post something. This will take a few years.

* Go to 1 meetup/month. Talk to people there, but don't make plans outside of the meetup. This will take a few months.

* Write something regularly. Create a newsletter from it. This will take a few months to years.

* Post to HN anonymously. Keep making insightful comments. This will take a few weeks to months, depending on your level of insight.

All of these will grow your professional network without excess social activity.

[sys_prog]

I find it hard to believe people meet trough hn comments. How many times did it happen to you?

[mooreds]

I have only met a few people IRL via HN, but have definitely built my network through it. That is to say I've built connection with people that I either met on HN and then connect with elsewhere online, or met them in real life. In one case I interacted with someone on HN, then helped them get a job, and then later they wrote something for my company, then we have interacted several times on LinkedIn.

Maybe I misread your comment, but I don't think that meeting someone in person is required to build a network.

[datadrivenangel]

Judging from their profile and posting history, I suspect a lot.