+1 for not allowing announcements as stand-alone items. There are indeed other and better channels for that. Having said that quite a few security incidents (get a cute name, their own vanity domains and associated websites and) result in relevant on-topic Q&A's anyhow as people struggle with work-arounds and mitigating measures I.e. BEAST , heartbleed , poodle etc.

" Adding a comment to the to-be-migrated question linking to the original (so people on the destination site can easily close-as-dupe when it gets there)" won't work because comments that include a URL on the target site get stripped from the question upon migration

@JourneymanGeek hence the edit and correction from my earlier assumption :)

I could't have said it better myself.

IIRC "let me google that for you" links are/were blocked, but maybe that block is only on answers and not for comments. anyway, sometimes I notice that the problem people describe is more than sufficiently documented, but if only you already know the correct jargon/technical term. Please don't hesitate to point that out. This Q&A is only one such example although I would have left a comment rather than an answer.