When I type “the splodge, that…” or “the splodge which…”, Mr Gates’ grammar police insist on the AmE usage, which doesn’t allow for either of these comma arrangements. In this instance, BrE is different (albeit probably less “correct”) than AmE.

The company’s managerial employees who work in Connecticut will not be eligible for this benefit.

(The company has managers in all fifty states and wants to exclude only the people in Conecticut.)

The company’s managerial employees, who work in Connecticut, will not be eligible for this benefit.

(All managerial employees are excluded. And by the way, all of them are at the Hartford office.)

A lot of people might think that this is where the which/that rule of Fowler and so many others pays off with a big dividend. But it doesn’t do the job even if you respect it. People have forgotten about cases where a preposition precedes the “which”, which makes replacement by “that” impossible:

This does not apply to state holidays on which no employees perform their regular duties.

(It applies to all state holidays, except those very few when absolutely no one is at their post.)

This does not apply to state holidays, on which no employees perform their regular duties.

(It doesn’t apply to any state holidays. And by the way, on state holidays nobody is working anyway.)

Your advice is exactly right: avoid being caught in a place where your only hope is to get a judge who correctly understands the punctuation rule and semantics for relative clauses. The examples above reflect the truth about English grammar; but God help you if you are forced to rely on the comma distinction and nothing else, because some damn fool will say he can’t see the difference. So re-draft!

I would put “no punctuation” on about the same level as using the word “witnesseth” in contracts, or using engrossment paper with red lines down each margin (not sure if this one will mean anything to your US readers).