In their legal parts it is non-capitalized:
https://www.hornbach.nl/services/algemene-voorwaarden/
But most of the site uses HORNBACH

However, if non-capitalized it should also be reported to NSI as this database (which iD probably uses) is capitalized: https://nsi.guide/index.html?t=brands&k=shop&v=doityourself&tt=hornbach
Even though this was intentionally changed: https://github.com/osmlab/name-suggestion-index/commit/8a843887e836b172c10d7f2800423814757292e3

Can't find any discussion about this though...
