MusicBrainz 'Special Purpose Artists' (SPA) are not related to any specific artists, style or taste. This means they are not suitable for recommendations, based on a user having listened to them in the past. For instance: [anonymous], [no artist], [unknown], etc.

A list of SPA to be excluded can be found here: https://musicbrainz.org/doc/Style/Unknown_and_untitled/Special_purpose_artist

The exceptions may be the [Disney] and [church bells] SPA, which relate to specific interests and don't have too many releases attached.