Can I eat a sauce that ruined my carbon steel pan seasoning

Personally I would avoid eating that sauce for the following reason.

The seasoning on your pan is basically a bunch of polymers which were created when you heated the flax seed oil to a very high temperature. https://en.wikipedia.org/wiki/Seasoning_(cookware)

When you "disolved" your seasoning in your sauce those polymeres are what went in to the food. I would recommend not eating those for the same reason I would not recommend to eat food fried at a high temperature in low smoke point oil (such as flaxseed).

You have some misconceptions here.

First, coconut milk doesn't neutralize any acid, it is just fat in water, probably with a very mild acidic pH itself. For neutralizing an acid, you need a base (and it has nothing to do with the perception of diminished sourness coming from eating fat alongside the acid).

Second, it wasn't the acid that stripped away the seasoning. Bases strip seasoning, acids don't. And you need something a lot more corrosive than an edible sauce for that. The advice to not make highly acidic sauces in iron pans is connected to concerns about rusting the pan underneath the seasoning. Your seasoning probably went away because flaxseed tends to make nonrobust seasoning.

As for the safety, it is obviously safe in the strict sense, polymerized oil gets created in everyday cooking too and nobody has created a regulation forbidding us from serving food where that has happened. This means that you won't keel over from food poisoning tomorrow. If you are asking it in any other sense (e.g. whether it has long-term effects on your health), this is a topic which is explicitely excluded from discussion on our site.