Spoiler tags not available in replies

Hello! How do we use spoiler tags in replies? The exclamation point in a triangle shows up here in the compose menu for a new discussion, but not when we are replying to an existing discussion.

The example given in the instructions for spoiler tags was when a user is asked to provide a lot of detail in response to an issue. But that user wouldn't actually be able to spoiler their detailed information, as things stand.

PS I just discovered, when searching this forum to see if anyone posted on this issue already, that when you search the forum for "spoiler" you get results for search term "forum"... I guess that's a bug too?