I wonder what the risks of publicly sharing one's USCIS Receipt Number (e.g., IOE9739418910) are.
Case number is not secret. It is listed on all the USCIS mailing (often visible through envelopes), it is listed on your USCIS-issued documents, visas, etc.
It is not directly identifying you anywhere outside the USCIS computer system, and the biggest risk is that someone may want to contact USCIS to impersonate you using this number and other pieces of PII they may have collected on you. But for what cause? Hard to imagine.