I considered Solana. Lower fees allows for micro tipping. Polygon is pretty cheap though, less that 0.3 cents at current prices. Its the sort of app that really needs to stick to one chain to save confusion and complexity, I think.

The problem is Polygon's general unreliability and lack of end users. Almost no one I know ever has any cash on Polygon. It's either Solana, ETH, or something like Arbitrum

That's interesting. Sites like DappRadar show far more Polygon apps than Solana apps (https://dappradar.com/rankings/chains, https://www.alchemy.com/dapps). I don't know how representative that is though.

I've noticed occasional issues with Polygon, which is frustrating, and some intermittent viem/Metamask errors that I only seem to get with Polygon. I've put it down to the immaturity of the web3 stack for now but it needs to get better.