My favourite pull requests are PRs that are obviously correct after you've read the description.
miniblog.
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One cute feature of markdown I'd not noticed before: there's no syntax for images *without* a description (i.e. alt text).

I'm a fan of simple issue trackers. A description, comments, and maybe a small integration with something.
Given this, perhaps it makes sense to build your own? You get a bespoke solution, and focusing on your main project prevents feature creep.
A search engine devoted to finding misspelled items on eBay! https://typohound.com/
I have sympathy for the Amazon model where pages are organised around specific products (i.e. aggregate by SKU). It saves every seller having to carefully write a generic product description.