Hello, Martin! It appears as though the forum does not include a spoiler function. i.e.; a text code that makes the selected block of text unreadable at a casual glance and requires a reader to intentionally reveal the contents.
Several times I have wished to put something under a spoiler, particularly in DMs with readers of my stories who ask probing questions and I wish to give them the option of a second chance to not spoil a revelation without the need to send them a DM asking if they are really really sure and waiting for a response before sending or not sending the answer.
I would think that spoilers should not be difficult to add to the forum, but in truth I don’t know. They have become common in various forums over the years. Perhaps this forum already has that function but the needed text code is simply unusual.