Full Text Search Coming
Note, the functionality of this may change – the feature is still in development and the specifics of how it works might be different when it's released to how it currently is set to work in the PR and as described below.
An upcoming patch for Mastodon, which is currently in the testing phase, will introduce federated cross-instance full text search (meaning, you could enter the word 'watercolours' into the search box and see any public posts from discoverable profiles from your instance and other federated instances that have used the word 'watercolours' in the post).
This is dependent on having ElasticSearch (ES) enabled, which mastodon.art does not (by choice, currently). So, here's a hypothetical scenario:
.art does not have ES enabled .other DOES have ES enabled .art user enables discovery, makes a public post, this post federates to .other that post is now searchable on .other But because .art does not have ES enabled, .art users can't use the search feature.
So even if your instance doesn't have ES enabled, this doesn't mean that your users won't be affected by this new full text search implementation.
How it will work:
On instances with ES enabled, the public posts of profiles that have the 'suggest account to others' box ticked WILL be indexed for text search.
Unlisted posts will NOT be indexed, regardless of this setting (but note that unlisted posts also don't show up in any of the public feeds (local/federated timelines) and won't be included in hashtag search results, so if you want to make a post with hashtags and want people to be able to find that post by searching for the hashtag, it has to be made with 'public' visibility).
Here's what you need to do to opt your content OUT of being indexed for full text search;
https://mastodon.art/settings/profile (substitute with your own instance URL if you're not on mastodon.art) > uncheck the 'suggest account to others' box.
With this checkbox unticked, even if you make public posts, they will not be indexed.
You can also turn the checkbox on, which means that any posts you make with the 'public' visibility *will be indexed, but posts made with the 'unlisted' visibility will not be indexed.
There is currently no way to have your account be discoverable (i.e., to be recommended to others via the Profile Directory, https://mastodon.art/directory) while not being indexed, unless all of your posts are made with the 'unlisted' visibility setting; with the current iteration of the feature, it's all or nothing. So unfortunately, if you want to entirely opt out of being indexed, you'll also have to sacrifice some discoverability of your profile.
There are other opt-in profile discovery directories you can use instead, though:
https://fedi.directory https://fediverse.info https://communitywiki.org/trunk
It's also important to note that currently, anyone who has the checkbox enabled but who doesn't see the updates about the scope of that checkbox changing to include opting in to search, will be opted in by default just by virtue of not being given a heads up to uncheck that box.
Relevant info for techier people than I:
The PR: https://github.com/mastodon/mastodon/pull/26344 One of the devs saying it's likely to make it into the 4.2.0 release: https://oisaur.com/@renchap/110856034083717387 The 'discoverable' setting: https://github.com/mastodon/mastodon/pull/23808 https://github.com/mastodon/mastodon/blob/4caa9f0e69f922ce70af50d695cc84a7f551534f/app/services/activitypub/process_account_service.rb#L117
Post talking about various issues with search and why it should be opt-in: https://www.anildash.com/2023/01/16/a-fediverse-search/
I'll do my best to answer questions, you can find me at https://mastodon.art/@curator ! :D
Massive thanks to other instance admins and to Hugo of MastoHost who helped me gather all of this into this post, who've been tracking the GitHub, fact-checking in the official Discord, and feeding back on the info that's in this post <3