Who does this scam accusation concern?

The 'SIGT' Signatum coin project.
Updated: The new moderated thread for the scam 'reboot'

Why is it considered a scam?

Because it bears all the usual hallmarks of every other shitcoin pump and dump operation that has gone before, from forum accounts routinely posting false claims of 'insider news' about major industry interest, to insanely high trading volumes on YoBit exchange which are abnormal for a coin lacking in any useful tech or innovation.

It was launched in July off the back of claimed technical innovation:

But the only feature it apparently has is a supposedly 'ASIC resistant' algorithm which, as any person knowledgeable in cryptocurrency would know, is only relevant for coins which are pure Proof-of-Work (PoW) based. This coin, however, has but a 100-day period of PoW before it is due to switch to Proof-of-Stake (PoS), which means the entire basis for its claims towards innovation are utterly irrelevant.

Its 'whitepaper' is devoid of anything of substance, bar for the repeated reference to said 'ASIC resistant' algorithm and is, clearly, merely designed to fool those new to this field into believing it to be a coin with technical and potential value.

In its OP it also attempts to claim that a 'user' (not a 'team member') has written an article on it, in an attempt to imply again industry interest which doesn't exist. That 'user', however, and their website, is simply just another layer of the fraud:

Its ANN thread Is currently being swamped by scammer sock-puppet accounts attempting to bury this information exposing it as an obvious pump-and-dump scam, which of course simply serves to prove it is not a legitimate project.

Avoid at all costs and, more importantly, learn to spot the signs of these scams, they aren't exactly subtle but newbie FOMO and inexperience means that these scumbags are often able to fool many into parting with their bitcoin to buy or mine-and-hold these useless coins.