Imo this is something narcissistic people do, not sure why borderline people would abuse retail workers out of the blue? They usually explode on people they're in relationships with, fueled by rejection, whilst narcs seem to blow up over anything where they don't get their own way.
Not saying you're completely wrong, just curious on your reasoning. To me, Lou treating retail workers like dirt just further solidifies my perception of him being an entitled narc over an asshole borderline. The main reasoning being the lack of actioning on his threats and lack of self harm. Lou always threatens to hurt himself, but there's never any evidence of him legitimately going through with it, it's just a tactic to get what he wants. People with borderline don't usually have the level of impulse control to not act on the threats they're putting out- they're more likely to act and then use the action as the manipulation tactic. Its more of a slash the wrists then say "look what you made me do!" kind of affair, or very targeted, personal attacks on a specific individual they have gotten extremely attached to.
Narcs on the other hand don't really make those connections. Its all so very surface level because there's that lack of empathy for others, so when someone doesn't live up to their expectations they have no qualms in attacking them to get what they want.
Borderline: "please I love you don't do this to me. I'll die if you leave me I need you. Look! If you walk out that door I'll take all these pills! Fuck you, I hate you. Get the fuck out of my sight"
Narc: "you obviously don't love or care about me, I give you everything and you treat me like this? I can't always be in the wrong you know, you need to take responsibility for how you make me feel!"
I doubt Lou would ever actually act on the threats he makes. If he really felt the way he did, he would keep the suicide bait tweets for extra sympathy and not delete everything to make himself look like an angel when he realised he's fucked his reputation again.