You can't "stake" bitcoin, like you can with some altcoins to try and earn coins if that is what you're thinking

What users are doing here is staking their bitcoin address for future reference... the idea being that by digitally signing a message using the private key for that address, they are proving "ownership" of the address.

In the future, should their account get hacked/locked or they want to do a trade/deal with someone who wants proof they're the "original" account owner and not an imposter on Telegram etc, they can prove their identity by signing a message using the same bitcoin address/private key.