LGTM. It feels a little like over-reach on the part of the BL to be saying how people lay out their page. If you were using a bulleted list with foo: bar colons for everything else, writing "ISSN:" instead of "ISSN" seems reasonable, for example. If the string beginning "ISSN" is intended as a computer format, that would be a different matter. Interesting that they insist on the string appearing even in non-latin script language countries, eg. Japan: https://www.ndl.go.jp/en/data/issn/index.html

All that aside, thanks for the edit @edent :) BTW I followed your example a couple weeks ago and applied for an ISSN for my own (much neglected) blog, and it arrived within a few days.