Got it. This is how federation works.
You need the local ID for the status you’re replying to. https://mastodon.social/@jkreeftmeijer/101236371751163533 is posted on https://mastodon.social, but you need the ID from https://mastodon.technology/web/statuses/101236371815734043 when posting a reply on https://mastodon.technology, for example.
To get the local ID for a Mastodon status on another instance, use the search API (https://docs.joinmastodon.org/api/rest/search/), or the search bar in your web client.
Searching for a status URL (like https://mastodon.social/@jkreeftmeijer/101236371751163533) returns the status on your instance, including the local ID.
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!