[logfromblammo]

Presumably, one can assume that once it is published publicly, someone else could make a note of it, and tattle on the author whenever they delete a hash without revealing the source of it.

In practice, nobody is attending to anyone that closely, aside from a handful of public figures, and shenanigans like those you described might actually work to get someone more attention, only to fail once they have enough. That's why a publication mechanism that disallows deletions is desirable for such hashes.