pineapple

 pineapple  is a common symbol meaning "welcome" and can also be sent in emoji form as a means of saying “hello,” “welcome,” or “aloha”.

Mastodon
Just after the beginning of the wider spread adoption of Mastodon, user @acw began posting pineapple emoji on the site and gave it the connotation of the following additional meanings as delineated in
 * Sending 🍍 to new people as a form of “hello,” “welcome,” “aloha”
 * 🍍 is the emoji shorthand for boost, a Mastodon specific name for repost
 * 🍍ing is also a form of Internet slang for when your Mastodon follower count surpasses your Twitter follower count.
 * 🍍ing is also a form of Internet slang for when your Mastodon follower count surpasses your Twitter follower count.