@JordiGH The citations aren't for checking whether the fact claimed to be true really is. They're there to show where the proof came from (see https://en.wikipedia.org/wiki/Wikipedia:No_original_research for the prohibition on writing novel proofs). Most mathematical claims in Wikipedia articles don't have proofs attached, but they have citations to sources where proofs can be found. When a proof is included, my feeling is that it should be included because it illuminates, not merely because it convinces you of the truth.

0xDE@11011110@mathstodon.xyz@JordiGH That said, I can point to instances where I've added proofs I made up myself rather than finding proper source. E.g. I added the proof in https://en.wikipedia.org/wiki/F%C3%A1ry%27s_theorem in 2006, but the oldest published source I've found for that particular proof is dated 2010. Fortunately the 2010 source didn't credit Wikipedia for the proof (as that would have disqualified it as a source) Probably these days I would try to choose a simple published proof rather than rolling my own, to have something to cite.