Tech account is an account played for another accounts benefit, built to be raided by 1 single account or 1 single alliance.
Different from multi how ? It has a player and not played via proxy.
To clarify the point here, I believe there used to be a rule which stated each account had to be played to its own benefit. Is that correct? Was that rule dropped, allowing multiple people to essentially use multiple accounts to the sole benefit of one?
Previously a multihunter would have punished such accounts, but I assume they found it too much work so just allowed this practice to happen, and the term 'tech account' was invented?