This is a really horrible idea for a number of reasons.
1. If you are going to send a check in the mail, please use a security envelope. Do not use envelopes made for sending letters (you'd be surprise how many people still make this mistake). Learn how to write addresses on envelopes and use the appropriate postage because USPS will send your envelope back to you if it isn't done correctly.
2. The USPS isn't exactly known for integrity and yes people working for the post office do steal mail and packages of monetary value. So you run the risk of some greedy person working for the post office realizing there is a check in an envelope and steal it and then cash it in somewhere and you've just been robbed (this is why you use security envelopes to make it far less likely for someone to figure out there is a check in the mail). Don't depend on the Postmaster General to guarantee your mail is safely delivered to Jersh because fraud still happens.
3. If you choose to send Jersh a check in the mail, know that you are running the risk of putting your dox out there. Return and sending addresses will be known to Jersh so he will know where you live. If you do something that rubs Jersh the wrong way, he will use your dox against you. Jersh has a very short temper and has a nasty habit of banning people for the dumbest reasons ever; if you send money to Jersh then you are risking this and it's on you.
4. There is no guarantee your money will contribute to Kiwi Farms. For all you know, Jersh will use your money to buy a Rolex.
5. There is no way of knowing how Jersh will treat your money in general.
6. Jersh or the people working for him may screw with your bank account if they commit check fraud on their end (which is a massive headache to deal with where you have to explain to the bank and potentially the police on why a check in your name seems part of something suspicious). To quote Biggie Smalls from his song Ten Crack Commandments, "Number 3: Never trust nobody. Your moms'll set that ass up, properly gassed up. Hoodied and masked up, shit, for that fast buck. She be laying in the bushes to light that ass up!"
7. It's fine if a small time website owner asks for donations and it's preferred that they accept cash, Google gift cards, or crypto. Once they ask for checks, that will raise a lot of red flags and it's bad OPSEC to start using your real world banking details to make a donation to an unproven merchant or beneficiary.
You have to be fucking stupid to send Jersh checks where he can use the money on who knows what or even blackmail you for any reason.