(I was debating whether to put this in the changelog discussion or make a separate thread, but since the rule has been added a couple months ago, and is pretty important, i'm going to make a separate thread)
Back in forum #176795, a new rule was added to BURs:
Aliases must be used for tags with more than 200 posts. Renames can't be used for tags with more than 200 posts.
As far as i know, this rule was added without previous discussion. I think the main purpose behind it was to lessen the amount of missed searches of popular tags.
The problem i'm seeing is that some disambiguation tags are getting aliased, which i feel causes more harm than good. In topic #17953 and topic #17788 other BURs were made to override the rule, which makes me doubt the rule's usefulness.
I also doubt the usefulness of the other limiting rules, such as the post count requirement. Reverse_bunnysuit is, unsurprisingly, much more popular than reverse outfit, but under the current rules, it can't be aliased. It could be argued that it's because of this that the rule was made, to avoid having a flooded tag, but it's also true that you could just search reverse_outfit -reverse_bunnysuit.