Hi @EricCousineau-TRI, thanks for all the suggestions, keep them coming!
For specific punctual suggestions, I suggest ticketing issues on the relevant websites. The GitHub - gazebosim/sdf_tutorials: SDFormat documentation and proposals. you linked to is a good place, as well as this one for generic Ignition documentation:
If you’d like to start a high-level discussion about the direction of the documentation in general, you’re also welcome to start a new topic here on Gazebo Community. Note that this specific topic, as well as some other topics, have been initiated by applicants to the Google Season of Docs (GSoD) program.