Specifically, the sender is referring to an issue or discussion found at this link: GitHub Issue #140. The discovery seems noteworthy, and the sender expresses a positive reaction to it.

Unfortunately, without the full content of the email, it is not possible to provide a detailed summary or additional context regarding the nature of the discovery or its implications for the Miniscript project. The link provided suggests that the issue might contain technical details or a conversation among contributors which could include bug reports, feature requests, or general enhancements related to the project.

Miniscript itself is a language for writing Bitcoin scripts in a structured way, aimed at improving the readability and analysis of scripts while retaining compatibility with existing Bitcoin script execution. The specific issue mentioned could relate to any aspect of this functionality—ranging from optimizations to syntax improvements or discussions about the underlying logic or security considerations.

To gain further insights into the significance of this discovery, one would need to visit the provided link and examine the contents of the GitHub issue #140 thoroughly, including any code changes, comments, and resolution steps taken by the contributors of the Miniscript project.