Overview
Evaluation tags (評価タグ, hyōka tagu) is one of the kind of tags on pixiv. Adding these "positive" meaning tags yourself is not a violation of the terms and conditions, but it is also not encouraged, as it tends to be treated as self-promotion (self-tagging).
Although these template-like tags are meant to praise the author, the criteria for judging them are solely subjective to the tag editor, and there is a lot of bias among tag editors and illustration contributors who receive tag edits.
They also have the detrimental effect of filling the tag field, which has a limit of 10 tags, with similar multiple tags, less searchable tags, etc., reducing the functionality of the tag field.
Also, be careful with the users bookmark tag, which includes elements that may bias a large number of people toward viewing the site. If you delete other tags because you want to add this tag, you may be considered a troll, so please use moderation.