I don't know why some of the flagging options are missing when I want to flag a question. By missing, I mean they are not there. Sometimes, the SE allows me to flag twice with two distinct messages, and sometimes it only allows me to flag once. This appears inconsistent. I don't get it. How does this flagging system work?
The official documentation for the flagging system may be found in the help center:
Flagging is a way of bringing inappropriate content to the attention of the community. The currently implemented flag types are the following:
- Spam (i.e. undiscriminated bulk advertisement)
- Offensive, abusive, or hate speech
- Not an answer (answers only)
- Flag to close (questions only)
- Duplicate question*
- Off-topic (with sub-reasons)*
- Unclear what you're asking
- Too broad
- Primarily opinion-based
- Very low quality (i.e. no amount of editing can salvage the post)
- Other (needs ♦ moderator attention)
* note that because flagging a question as duplicate or off-topic auto-generates a comment on that post, these options will not appear in the flag menu until you have earned 50 reputation (the amount required for commenting).
Notice, in particular, that "Not an answer" (NaA) and "Flag to close" (FtC) are restricted to answers and questions for obvious reasons.