They should sign an ethereum address to reduce ambiguity
(Any crypto asset address is fine, even PGP is good enough for this but PGP had 25 years to make that user friendly and common but failed, and cryptocurrencies made signing software more prevalent and uniform wayyyyy faster)
Remember when satellite.earth "pioneered" this idea for their platform? (not ragging on them but some of the content posted on there were insightful and unique)