Please include information requested at https://github.com/ValveSoftware/steam-for-linux so we can gather additional information.
What OS are you using? Moreover, are you on a wired network or wireless?
I can't repro this. Does it happen every time for you? Are you doing anything in particular beforehand that might affect things? Can you post system info for your friend also?
If it's wireless, that may be part of the issue; I've noticed that sort of thing on some wireless networks.
Can I just say this happens whenever the person I'm talking to also has Steam for Mobile running at the same time (hence probably similar to the wireless network mentioned above).
So I'm not sure this is Linux client specific.
I'm not able to repro even when chatting where one person also has a mobile login. We'll keep looking.
I just witnessed this with a user who was using http://steamcommunity.com/chat/ do the same thing.
Every time a user goes to that site, it marks them as online, even if they already are. If Mobile works similarly, it may have that same function.
It doesn't seem to change status if you refresh or full refresh (Ctrl+F5).
I don't see it with web chat either. Logging in to chat there didn't produce any status message in the client chat.
There we go, finally got it to happen. Should be easy to fix.
The next client will have a fix for this.
Nothing extracted yet.
This is a really strange issue. My friend's chat is spammed with these over time:
OrangeRain is now Online.
OrangeRain is now Online.
OrangeRain is now Online.
OrangeRain is now Online.
OrangeRain is now Online.
OrangeRain is now Online.
OrangeRain is now Online.
OrangeRain is now Online.
and I, nor he, knows what is causing it. Yes, it's a beta but this doesn't happen while running Steam on Wine, so I think it's a Linux issue.