Even if/even though comma

I'm having difficulty explaining how even if /even though sentences are punctuated (in the middle of a sentence).

The basic rules should follow the rules for subordinate clauses and restrictive elements. which would be:

Cobuild Grammar Plus:
Use no comma before a subordinate clause (often beginning because, if or when) at the end of a sentence if it is essential to the meaning of the sentence:

Nonessential clauses (often beginning although, even though, or whereas) take commas.

Chicago Manual of Style:
If a dependent clause is restrictive—that is, if it cannot be omitted without altering the meaning of the main clause -- it should not be set off by commas. If it is nonrestrictive, it should be set off by commas.

1. Paul was astonished when he heard the terms.
2. At last she arrived, when the food was cold.

This is basic rule and the examples given in CMOS are clear cut examples of non-restrictive sentences. But, almost all the examples I see in dictionaries use commas but do not appear to be non-restrictive. Can anybody offer more information on this? (Note: CMOS do add that deciding on which to use is tenuous and that a comma should be used when in doubt).

Thanks.