Are there an limitations imposed by Florida FS718 as to who can serve as a proxy? Specifically, is there any reason a non-owner can not serve as a designated proxy?
First, a question: Is your community organized as a condominium or as an HOA? I’m asking because you say HOA but you quote from the Condominium Act. In Florida, HOAs do not run condos; in Florida, the governing body of a condo is called a Condo Association, not an HOA. Under Florida law, condominiums are subject to the Chapter 718, the Condominium Act, and HOAs are subject to Chapter 720, the Homeowners Association Act. Because these Acts impose different requirements, it is important to be clear which applies to your community.
To answer your question, both the Condo and the HOA Act allow proxy votes, and neither imposes restrictions on who may act as a proxy. However, it is possible that your Association's Bylaws do impose restrictions, so you need to check them. Moreover, the two Acts do impose different restrictions on when proxies can be used, what form they must take and so on. So you really do need to look at the relevant Act.
Please Note: In trying to figure out what legal rules apply to your community, you probably need to do more than just read the relevant Act. That's because the law-on-the-books seldom gives a complete or accurate picture of law-as-applied. To find out what rules really apply to your condo, you may need to do more focused searches on line, or even talk to a Florida attorney.