As I recall, the forum software now used (“new” forum) is a third party product. Some things like ignoring a specific poster are no longer available and Blizzard may not have enough control to add that functionality. Stickies apparently do not work the same way as they did in the past as they do with this vendor provided software. Some of the keyboard shortcuts (click the three vertical dots next to your avatar in the top right corner of the screen and the option is at the bottom of the dropdown that appears) that should work do not. As I posted elsewhere:
Other than the above, maybe asking again about stickies in the Website Bug Report forum? May not be the exact place needed to be posing that question but that’s my best guess.