Actually, voting shares can be lent out, but it is just that the lender will not be able to vote while the borrower can. (Exception is if the shares are lent out on the record date, in which case both the lender and the borrower can vote. ) Reference: https://www.mcgill.ca/desautels/files/desautels/Cgmr0704.pdf
The implication is that the number of shares recalled from the shorts prior to the record date depends on the lenders.
you can’t vote the same shares twice.
companies like mediant and broadridge, and recently a startup called say, handle this for brokers and their clients.
they know what each brokers record date settled position is at dtcc and when the brokers submit all their clients votes they must match.
if you don’t hold your own fully paid shares on r/d for a proxy vote, you can’t vote. focus on fully paid shares only, not margin shares. margin shares can go either way depending if your broker has them loaned or not on record date. it depends on your brokers seg requirements on that record date vs what they have loaned/borrowed, vs internal shorts, and if that calculation leaves free excess position in their dtcc custody account, which can be voted.