... someone (possibly the same people, or new people) began mass modifying the tx of OTHERS. This particular event has no direct ecnomic value and your right it is likely griefers, or someone looking to damage the credability of the Bitcoin network. ...
What I still do not fully understand is whether capturing and manipulating the transaction ID of a transaction would result in neither the original nor the modification making it to confirmation due to the perception of a double-spend attack, or would one win out and in all cases the desired transaction is accomplished.
The former constitutes a potentially severe DOS attack. The latter would not be that big a deal (in my own use-case and as far as I currently understand.)
Or is it the case currently that the end result of an intercept+modify_hash+redistribute attack would be somewhat left to chance due to differences in the protocol implementation and such-like.