there are some badges that can be awarded multiple times.
when I choose another badge to monitor, those I have already achieved, even if they say they can be awarded multiple times, are not available on the selection. Is this a bug? why these badges cannot be monitored?
I don't see why they can't be monitored, as they can be achieved multiple times.
If you think about why Stellar Question and Nice Answer are awarded, you don't need to track them per user--they are implicitly tracked on every post. Each question knows how many favorites it has. Every answer knows how many upvotes it has. That is the tracking.
When a question hits 100 favorites, that triggers the Stellar Question badge to be awarded--to the person to posted the question.
To watch your progress on these types of badges, look at your questions where this is implicitly tracked on every question.
Think about the badges with progress meters. They are tracking a simple count of events per user. The logic is a straightforward tally.
To track Nice Answer, would there be a progress meter for every answer? (This would get busy if you answer many questions)
One that tracks your top answer? (The answer being tracked could change over time, as you create new answers.)
Should it track the next award? (now you need to get the max of the counts, but exclude answers that already have the badge tied to it.)
Ultimately, tracking these badges that are awarded multiple times requires different logic (both a different way of counting and a different way of displaying).
That logic simply doesn't exist. The first question is should those badges have per-user progress meters. Then, you would need to determine the "best" way to count and display the badges.
Until then, these badges can't be tracked using the current progress meter implemention
When I open my Next badge suggestion list in any of my profiles, I can see not a single badge there that is from among those awarded per post, like e.g. Stellar Question or Nice Answer. I don't believe it's because I've achieved them, as, for instance, on DBA.SE I've currently got the latter but not the former – and I can see neither in the list.
I can't authoritatively explain why that is so, as I'm not a Stack Overflow employee and have otherwise no access to information of this kind. Still, if I'm allowed to speculate then my guess would be, those badges may just be too expensive to track. I may well be mistaken about the reason, of course, but the main point is, I doubt their absence is a bug. Rather, it must be by design.
Badges awarded per post are not the only kind that you can get multiple times. There are also badges from the Other category – Announcer, Booster, Publicist – that have the same property. I imagine they are even harder to track, which is probably why they are excluded from monitoring too.
Could it simply be that that the ones awarded multiple times are the ones that you have no control over because they are to do with the cumulative actions of others, so it makes no sense to track them
