I've set up a site called https://whystartat.xyz. My aim is to collect ambiguous, inconsistent, or just plain unpleasant conventions in mathematical notation.
It's a wiki, so you can edit it. Please add in any examples that come to mind!
@christianp This is great!
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!