For HN, you could map the drop-down contents directly to submission guidelines:
- Poor/incorrect title
- Non-original source
- Promotion/spam
- ...
Especially when some things feel like they should have a low threshold for flagging (if 2 people agree it's obvious commerical spam, or terrible-quality content, or a duplicate submission from the past 48 hours), while others feel like they should have a higher threshold (e.g. if 5 people agree it's off-topic for HN, or a threshold proportional to upvotes).
https://news.ycombinator.com/item?id=40958364
Like others in the thread, the first time I looked at my list of flagged submissions, there were 20+ just random things on there that I had obviously just fat-fingered on mobile.
Back then I decided to never upvote anything, because hitting the wrong arrow was so easy and that I figured no votes was a better contribution to the site than frequently wrong direction votes!
It's fairly rare now that I accidentally click anything other than a (thankfully easy to reverse) up or down arrow, but I still 100% agree that anything like "hide" should be easily reversible.
I think the main reason is the Web1.0 design of HN doesn't translate well to small screens.