@timbray for testing purposes with the clients I use: #coop #co-op #co_op #coöp #co~op #c00p #CoOp

Personally for clarity of (English) speech I like #co-op , for visual distinction I like #coöp . A distant third is #co_op . In writing this (with ivory) both co-op and co~op appear as #co plus punctuation and ‘op’