At my previous job, I decided to make a Slack channel named after one of the C preprocessor directives (#define I think, or maybe #endif). A handful of people found it and appreciated the joke.
But then, a few months later, one of the admins contacted me to ask if it would be okay to delete the channel. You see, in large organisations, Slack knows which channels are not meant to be visible to other parts of the org, and it was causing mentions of the C preprocessor directive to be censored for people outside my group ^^;
Since, as OP says, non-members occasionally could find the channel, it was probably a public channel. The people who complained were probably "multi-channel guests". They'd see masked-out channel names except where they are explicitly allowed.
Ah, no, they wouldn't have been guests. The organisation was large enough that it had multiple “workspaces” corresponding to different divisions. Channels always belong to a workspace, but some are shared between workspaces. You can only see the channels belonging to or shared with your workspace.
But then, a few months later, one of the admins contacted me to ask if it would be okay to delete the channel. You see, in large organisations, Slack knows which channels are not meant to be visible to other parts of the org, and it was causing mentions of the C preprocessor directive to be censored for people outside my group ^^;