At some point, we had the following text in the Grid Baseline section of the Grid Layout specification:

"A grid item participates in baseline alignment in a particular dimension if its value for 'align-self' or 'justify-self', as appropriate, is ''baseline'' and its inline axis is parallel to that dimension."

This text has been removed, but there is still a broken link to the baseline-participation. Either the broken link is an error to be fixed or we miss the removed text. In any case, I think the text about grid item's baseline participation is something useful, but perhaps I'm missing some other issue where that was discussed already.