What's going on?
Earlier today (Feb 2), the official Twitter account @TwitterDev announced some very important changes to the access to the Twitter API, revealing it would stop being free to use starting February 9th, one week after the aforementioned announcement.
This API is used as part of the Twitter binding method used in many games, Arknights included.
How does this affect us?
The official Arknights Staff account has announced that, at this time, they don't expect any impact from this change. HOWEVER, they HAVE recommended that players should rebind their account using other methods to avoid any unforeseen circumstance. This is probably good advice, since the exact details and ramifications of the Twitter changes are so unclear, it is outside the control of 3rd parties, and nobody really knows exactly what Twitter is going to do here. If your account is solely linked via Twitter, consider using other methods.