Bluesky has no formatting, so Unicode fills the gap
Bluesky posts are plain text. The post box has no bold or italic buttons, and markdown is not converted, so asterisks stay asterisks. That is why people search for Bluesky italics: the only way to get them is to paste characters that already look italic.
The italic and bold italic styles on this page are the closest match to normal emphasis. Use them for a single word you would stress when speaking, or for titles of books and films.
Counting and handles
Bluesky counts posts in graphemes, so each styled letter counts once toward the 300. You can style a line without losing room for the rest of the post.
Your handle is a domain name and cannot be styled. Your display name and 256-character description can, and they appear on every post and in search results for people, so a small styled touch there is seen often.