The tag is present in Lintian version 2.104.232. That is the most recent version we know about.
dpatch files should carry a description of the included patch. Description lines start with "## DP:".
As well as a description of the purpose and function of the patch, the description should ideally contain author information, a URL for the bug report (if any), Debian or upstream bugs fixed by it, upstream status, the Debian version and date the patch was first included, and any other information that would be useful if someone were investigating the patch and underlying problem. Please consider using the DEP 3 format for this information.
Refer to https://dep-team.pages.debian.net/deps/dep3/ for details.