It would seem that the moderators/creator seeks to use the merge function as a optional approach to collaboration proposals.
They might add an option for a ‘multi-authored’ post, but it will take time to implement.
For now @Nicole_C_Scott has the best suggestion for collaborative posts.
Moderation also said something about about focusing forum attention on proper formating for detailed contrubtions vs. observational posts. I recommended a guide, proposal roadmap for advancement, or pre-formatted post much like what shows up in your text box for merges, but geared at the enumeration of solutions and further ‘policy based format’.