Maybe the user is a spammer, but he hasn't broken any rules that warrant a DT red-tag in my opinion.
I'd second with your opinion.
Both of them are alts and participating in twitter campaign, but there's no forbid to use multiple accounts on the general bounty and twitter rules, they only not allow multiple accounts on signature campaign. So I wouldn't leave a negative feedback.
You can see that andrew_788 only copied the message to a BM from a previously left post of dwminer1. So he copied also the address dwminer1 uses. andrew_788 posted this address just once and only here.
andrew_788 posted on 39th pages while dwminer1 posted on 36th pages, how it's possible a copy paste mistake? looks impossible.
if you link your account together with an address here is not what's against the law, but participating the two accounts on the same signature or bounty campaign is forbidden
Both of the accounts are participating in the same bounty campaign, check the twitter campaign spreadsheet, you will see both of the users were participated. Since both of them participating in the same campaign, do you think it's forbidden? you can leave negative feedback to both accounts.