And so users with slow computers will simply stop using the platform, creating a centralisation of its own form - this is especially bad if difficulty is out of the control of the users, which in this paper it appears to be.
Low security transactions are secured once they are included into the graph, doublespending becomes hard after that point. It's a CPU vs bandwidth tradeoff. Users with very slow computers
and very slow Internet will indeed be unable to use the platform unless they cooperate with each other (via multisignatures).