So, let me see if I'm interpreting this set of non-sequential screen caps from deviantart correctly.
Between 2003 to 2004 it seems to be an ongoing series posts and comments between two DA people over a year. Mat-Kun and Animatrix.
Your suggesting that animatrix is Rebeca Sugar. The evidence for this is a post where she was logged in to her brothers "Stevens" (Steven Sugar, presumably) account accidentally and a piece of art signed "To Becca".
Not necessarily a smoking gun but ok I'll bite. animatrix goes on to write embarrassing but playful stuff about "wanting your fung-fu booty" and "wanting to molest and *glomp* mat-kun. This seems to be reciprocated.
animatrix and mat-kun flirt some more and she convinces him to draw some very soft yaoi stuff. He's not to into it, but it make her happy and he draws it. Then he has a rant about a software program not working and says he'll kill himself. It's implied that they have met and are bf/gf. Then a month after the yaoi conversation theres a piec of art that looks like it has blood on it and was made during self harm. animatrix expresses concern.>tldr
Its probably Rebecca's, and she probably had an internet bf who was in to self harm. Is it dark, yes. But it is a real thing that happens to real people. It's not like she was goeding him to "DO IT FAGGOT".
Is this supposed to be the new gamergate or something?