Thanks for this questions!
The initial reasoning for utilizing NFTs for Signaling is because the ERC-721 standard for non-fungibles provides a very seamless standard for not only being able to represent something unique on the blockchain but more importantly for these purposes the ease of being able to track all Signals on a Registry.
With the launch of Signaling there is also the
CSTRegistry-stands for crypto-spatial token registry, and it is a general purpose registry for registering
NFT s on the FOAM map. From a design perspective having Signals be represented as a NFT and then tracked on a registry made the most sense. Further, with this registry it allows any additional NFT to claim a location and be added to the registry. This could be related to FOAM or not, but then still be able to be displayed on the Map with added layer controls.
Additionally, as the design space for Signaling is left general and that rewards that Signals influence will be driven also by how old they are, there is a factor of time. There could be a scenario where an NFT of a Signal is more valuable than the FOAM tokens staked because of the added temporal component. More also here: https://blog.foam.space/signaling-on-foam-91626d858328