using TC REST API it is possible to trigger a build with a comment. Sush comment is shown next to the build. So it is handy to embed more data (metadata) to each build.
TC also support interaction with scripts using Service Messages. I was wondering if it is somehow possible to set the build comment using Service Message or any other way during build execution.
If you already familiar with TC REST API, then nothing can stop you from pinning/unpinning the build with a commment from a build step during the build. You can use bundled ant runner for this.