when you write stuff in the forum now, there’s an option to switch between a Rich Text Editor view and a Markdown Editor view. Markdown, HTML, etc. need be input in the Markdown Editor view. If you try to input that sort of stuff in the Rich Text editor, it’s going to escape special syntax in an attempt to turn your code into regular text.
see: https://forum.inaturalist.org/t/confusing-new-change/68253/2