I always feel bad when flagging something for moderator attention, because it's never important:
So what's the least annoying:
- pinging in chat
Personally, I think it depends on the case on which I would want you to do.
I personally prefer that if it's not ultra-pressing you just flag a post, then one of us moderators can take a look at it. And that's any moderator because we all share the same flags queue.
If it's something more pressing and urgent then ping us in chat.
This is, of course, my opinion - other moderators may have different preferences.
The notable exception being flagging in chat:
I'm not a mod, but my comment was too long for the box.
Flagging seems to me much more appropriate.
If you're pinging a mod, that means you're pressing that person to deal with it. Flags can be handled by any mod, so, no pressure is applied to anyone (in my culture, imho, the essence of true politeness is avoiding applying pressure to anyone!). It seems to me the annoyance factor of a ping, which makes an actual sound, is personal, and demands a response according to the rules of conversation (of course, one can ignore, but one is thus uncomfortably overriding a response learned in the first 8 months of life...), is infinitely higher than a flag in a queue which can be dealt with by any of a group of people at their convenience.
Also, flags are in the database, and provide justification, history and a train of reasoning for mod actions. They thus provide a level of transparency and data trail more effectively than chat messages. At the same time they are private, between the flagger and the mod team. This is in contrast with a chat message, which unnecessarily draws public attention to the person whose output is being highlighted as of concern (naturally I'm not thinking about spammers, but good-faith contributors).