The current [Slicer[Development] ] subject line prefix does not look nice: spacing is inconsistent, many square brackets, etc.
It would be also nice to be consistent with subject line prefix of GitHub notifications. For example, this is an email subject sent by GitHub:
Re: [Slicer/Slicer] WIP: Use header metadata to initialize volume scalar range (#702)
I think [SlicerForum/Category/Subcategory] would be a short and consistent subject line prefix, for example:
[SlicerForum/Support] Some subject abc abc
[SlicerForum/Development] Some subject abc abc