I'm playing on Blizz server ofc, or I wouldn't be bothering anyone with these issues 
The "LBVM" messages come from DBM_API\API.lua
It also modifies some WIM filter:
if type(WIM_Filters) == "table" then
WIM_Filters["^LVBM"] = WIM_Filters["^LVBM"] or "Ignore";
WIM_Filters["^LVPN"] = WIM_Filters["^LVPN"] or "Ignore";
end
Oddly, I *do* have a WIM filter for "^LVBM" to 'ignore', perhaps I'm mixing up various alts with different settings... I'll pay closer attention to it next time I see the whispers.