What are the default filters? Or is default to show all contributions (no active filters)? I see no "default" button for a pre-selected list of active filters chosen by the wiki admins. If default is to show all contributions, then I believe many editors will stop using their watchlist very much, if at all.
Anyone with a lot of categories on their watchlist may give up as I almost did before someone selected some filters for me. See my other thread. The filters are baffling, even to longtime editors. The "all contributions" watchlist shows all the many files added and removed from those watchlisted categories. That makes the watchlist very long and almost useless. One can't find the important stuff buried among the files being added and removed.
A pre-selected fallback list of active filters might keep many editors from abandoning their watchlist over time. There needs to be a filter to show all revisions, except for revisions for talk pages. The filter should set talk pages to latest revision. Otherwise the same active talk pages will show up on every day of the watchlist. I like seeing all revisions (for most things), but had to turn it off due to talk pages filling up my watchlist.