I completely agree with you.
As I wrote here , spam must NOT be deleted but it must SUBMITTED (and SHARED).
There are services that centrally collect the spam and implement their anti-spam checks using these central repositories.
So I believe that every missed spam should be reported, so that everyone can benefit from these infos.
Deleting the spam is just a temporary (and local) workaround.
For instance, Akismet offer this service, offering a public API to be invoked to post spammy posts (and their associated infos).
Q2A already has an Akismet plugin, but I think it's completely abandoned.
It should be enhanced to have this feature, displaying for instance a "spam flag" under every post (maybe visible to users with at least X points or with an admin/moderator role).
It would not be bad to have such a feature....