The developers of "vanilla" Mastodon also run mastodon.social and they kind of use it almost like a staging server for the software as published on Github, often running nightly builds. For example, last Sunday a build was pushed with a new layout for link previews where the link title was displayed in large text instead of inset in a box like it used to be. This change appears to have been based on a whim of the project lead and was immediately somewhat controversial (seemingly even with other members of the development team). Anyway, I noticed these title previews didn't seem to have a specific limit on their length.
To test, I created a test page consisting of a single line of text plus OpenGraph tags, whose OpenGraph title was the complete text of the Communist Manifesto¹. I discovered that in fact anytime you posted this link on Mastodon it would print the entire 6,000 line title in h3 text directly into the feed with no way to hide or collapse it. There's a video here showing how long this takes to scroll through (50 seconds).
The bug has been fixed as of this morning.
¹ Not actually complete, I omitted section 3 as it has complex formatting.
