Should the (s) in Header(s) be dropped, or added to Subclause too?

• Yes, we should consistently apply one style.
• If we use a vertically-centered style, we should do that properly (eg, \multirow rather than the current "put the text in the right cell, maybe off by half a row" approach)
• Yes, we should consistently either pluralize or not pluralize the column headings
• Also fix the summary table in [atomics.general] to remove the line separators between <atomic> entries

@zygoloid, thanks for your input. However, there are a lot of "if"s here. Here are my preferences:

• use first row positioning
• do not pluralize the column headings (we also say "Subclause", not "Subclauses")

@tkoeppe, any opinion here?

I agree with first-row positioning. Centering of any kind is "cute" but ultimately distracting. I also prefer staying on the baseline; on introspection I am finding this to be a rather strong preference.

I have no strong opinion on the plural issue, but I agree that the "header" and "subclause" columns deserve the same treatment, whatever that is. Plural may be a bit more accurate to how we end up using this column, but since many instances don't have more than one entry, a flat-out plural ("headers") might be confusing. But the parenthesized style ("header(s)") looks clunky, so I'm inclined to agree with Jens's suggestion to not pluralize.

Tangential: The overall visual style of the summary tables is abhorrent. I have a local patch to make my PDFs look less repelling; I'd welcome encouragement to propose changes.

Editorial meeting:

• Vertically aligned at the top (first-row positioning).
• Singularize the headings; just say "Header" always.
• Fix "atomic" table.
• Left-align "Subclause" heading with the title.
• Linearize the headers (make it a list, comma-separated). Sort the header list lexicographically.
• Remove horizontal lines between sections having the same set of headers.