Instagram is adding a new status indicator dot so people will know when you're online and ignoring them.
TechCrunch reported yesterday the green status dot indicates when a user is active on the app. Instagram says you'll only see status for friends who follow you or people you have talked to in Direct. The idea is to increase the time you talk to people you're talking to already.
You can disable the feature in the Activity Status part of the settings menu. It’s “on” by default.
Source: Tech Crunch