Perhaps, alhtough "person who you get an an argument with intermittently downvotes you posts" isn't exactly a "conspiracy theory". It's just a thing that does happen in internet communities, and that anyone who has moderated one has experience mediating.

But, it's best to be certain! To ensure my downvotes are truly deserved: my bet is on the temporarily embarrassed millionaires taking offense to the last sentence of my prior post ;-) (i.e., /s :) )