URLs based on the old filter schema (i.e., hide X), need to be supported under the new filtering mode proposed ("show Y"). As a general rule, a "filter X" parameter can be translated into a "show other items in the group apart from X". However, it is possible to add contradicting parameters in the URL (hide registered + hide unregistered) that cannot be directly represented in the new model.
For cases where the user reaches Recent Changes through a URL with contradicting parameters (e.g., bookmarked links, tweaking URL parameters, etc.), the idea is to communicate such situation to the user for the user to check the results correspond to their expectations.
- When the user reaches the page by using a problematic URL, a [[ https://www.mediawiki.org/wiki/Bubble_notifications | bubble notification ]] is shown.
-- The message indicates that "Contradicting parameters from the link you followed have been ignored. Please, check that active filters are as expected."
-- Bubble notifications are a standard component showing a message for a few seconds to the user and vanishing after that.
- The resulting URL (after the translation to the new system) should reflect the active filters shown after the adaptation, and sharing or bookmarking it should not propagate the message to be shown when accessing it again.
The messaging avoid technical terms such as URL to use a more familiar concept such as following a link. Although it may be 100% precise (e.g., advanced users manipulating the URLs themselves), seems adequate for less experienced users not to freak out when just following a link they found elsewhere (e.g., at the teahouse) unaware of their parameters.