The problem is that different news sites will code these in different ways, making it difficult to create a universal filter for them.
However, this is the sort of thing that uBlock Origin filters are for. If there are a handful of specific sites that are annoying you, you could create a callout filter for each site. You'd need to learn a little about how webpages work, but uBlock Origin has tools to help you out. This would be a lot easier than creating a browser plugin; uBlock Origin has done most of the work for you. Here's a tutorial to get you started; the Element Picker is the part you're looking for.
I think they're called call-outs:
https://www.prepressure.com/printing-dictionary/c/call-out
Does Reader Mode in Firefox get rid of them?
Can you give a few examples of pages doing this, for reference?
The problem is that different news sites will code these in different ways, making it difficult to create a universal filter for them.
However, this is the sort of thing that uBlock Origin filters are for. If there are a handful of specific sites that are annoying you, you could create a callout filter for each site. You'd need to learn a little about how webpages work, but uBlock Origin has tools to help you out. This would be a lot easier than creating a browser plugin; uBlock Origin has done most of the work for you. Here's a tutorial to get you started; the Element Picker is the part you're looking for.