I never heard that that I recall and I sure don't know how you could stand your ground from the codes. 

Now, having said that, if I saw porosity like that and the shop was not fixing it without me saying a word, it would be in my report and I would seriously question their desire for quality.

Brent

It is defined in 3.0 but I have never found it in D1.1 for Visual . Here is a commentary with it referred to but no information. https://app.aws.org/mwf/attachments/40/189140/AWSPorosity.pdf

Aligned rounded indications are addressed for NDE methods .

Gerald

I've also had a hard time believing you can have one porosity hole up to 3/8" in diameter in a linear inch of a fillet weld, or even two in 12 inches of weld.

I don't recall ever hearing about that formula for calculating allowable sizes of porosity.  I do go along with welderbrent with the idea that a responsible QC/QA department will generally repair items that may be within code, but could telegraph an image that would make a customer loose that ol' warm and fuzzy feeling when it comes to first impressions... and when a customer sees sloppy workmanship on the surface, it's easy for them to think there could be subsurface flaws as well. Most of the porosity I see on the job are single pores or smaller clusters, and when excavated they often size-up on excavation and can go quite deep, which can be another reason a responsible inspector will remind a responsible QC/QA guy that this scenario might exist.  I carry a couple of the smaller wires from a torch cleaning set and can sometimes wiggle that wire a good 3/16" into a surface pore.





I cut my teeth in RT in the 70's and there were plenty of times I'd see an acceptable diameter pore, but it would be so dark it was obvious it had some significant height to it, and I would recommend a repair. Here is a section view and etching showing a really nice elongated pore just under the surface, and below that is some surface worm tracking.

By decades, does that go back into D1.0 into first edition D1.1 prior to the release of D1.5 (71-74)?

Creative QC'ing comes into play.
With a measurement of depth that would indicate less than the desired throat dimension, then add the major axis of the opening, it is possible that you might come up with an "Under run" situation if it were the worst case scenario with <1/32" porosity yet with multiple occurrence. So in other words, after an intense amount of measurement you might could show that the sponge looking weld was not meeting the volume of desired weld material
If all else fails, it definitely would fall under the QC's judgement of Poor Workmanship Practice.

We have two conversations running side by side. The definitive points are Al's and third eye. Al clarifies the point that in D1.1 what we normally think of as porosity is not addressed AT ALL. Third eye makes the point that customer expectations are ALWAYS in excess of code mins.
The seeming negligence of the porosity determination in D1.1 is not a negligence at all. It is based on sound engineering assessment of the structural deleteriousness of porosity which is generally negligible.
Appearance is another issue altogether.