That means you probably switched to a different sort order for that favorite. You can change it by tapping the three dots on the right and choosing “Update sort” (in my case the resulting dialog box looks weird/buggy, but choosing “update sort” again lets me change the sort for that favorite, while choosing “cancel” on the far left removes the custom sort and goes back to the default of Active which also removes the icon you saw).
They’ve been terrible for years, I switched to 9to5Google a long time ago
One thing that might be Pixel-specific is it lets you adjust the selection after the initial copy, prior to pasting it elsewhere. One thing that may be more universal (maybe?) is copying from the recent apps screen (the one that shows when you swipe up partway and see all open apps) uses OCR so you can copy from anything, including apps that have normally blocked that functionality.
I don’t know if there’s an option for posts, but for comments I think this is what you’re looking for:
Old and busted: Twitter is the global town square
New hotness: X is the global town sewer