Why is Chapter 15 of the SN not 'Eternalism'?

Why is Chapter 15 of the SN not 'Eternalism'?

Key Pali words in Chapter 15 are saṁsāro, sandhāvataṁ & saṁsarataṁ. SN 22.99 shows these words do not necessarily refer "transmigration" or "reincarnation", as follows:

At Savatthi. “Bhikkhus, this saṁsara is without discoverable beginning. A first point is not discerned of beings roaming and wandering on hindered by ignorance and fettered by craving.

Suppose, bhikkhus, a dog tied up on a leash was bound to a strong post or pillar: it would just keep on running and revolving around that same post or pillar. So too, the uninstructed worldling … regards form as self … feeling as self … perception as self … volitional formations as self … consciousness as self…. He just keeps running and revolving around form, around feeling, around perception, around volitional formations, around consciousness. As he keeps on running and revolving around them, he is not freed from form, not freed from feeling, not freed from perception, not freed from volitional formations, not freed from consciousness. He is not freed from birth, aging, and death; not freed from sorrow, lamentation, pain, displeasure, and despair; not freed from suffering, I say.

Bhikkhu Bodhi translation

Worse, in MN 38, a bhikkhu named Sati was rebuked for saying a "same consciousness" roams & wanders, as follows:

Now on that occasion a pernicious view had arisen in a bhikkhu named Sāti, son of a fisherman, thus:

“tathāhaṁ bhagavatā dhammaṁ desitaṁ ājānāmi yathā tadevidaṁ viññāṇaṁ sandhāvati saṁsarati anaññan”ti.

“As I understand the Dhamma taught by the Blessed One, it is this same consciousness that runs and wanders, not another.”

Bhikkhu Bodhi translated; "rebirth" embellishment removed

As for the Pali word "sattānaṁ" ("beings"; plural), SN 23.2 and SN 5.10 define "satta" ("a being"; singular) as merely strong attachment and a view, as follows:

'A being,' lord. 'A being,' it's said. To what extent is one said to be 'a being'?

"Any desire, passion, delight, or craving for form, Radha: when one is caught up there, tied up there, one is said to be 'a being.'

"Any desire, passion, delight, or craving for feeling... perception... fabrications...

"Any desire, passion, delight, or craving for consciousness, Radha: when one is caught up there, tied up there, one is said to be 'a being.'

"Just as when boys or girls are playing with little sand castles:[4] as long as they are not free from passion, desire, love, thirst, fever, & craving for those little sand castles, that's how long they have fun with those sand castles, enjoy them, treasure them, feel possessive of them.

SN 23.2

Then the bhikkhuni Vajira, having understood, “This is Mara the Evil One,” replied to him in verses:

“Why now do you assume ‘a being’? Mara, is that your speculative view? This is a heap of sheer formations: Here no being is found.

“Just as, with an assemblage of parts, The word ‘chariot’ is used, So, when the aggregates exist, There is the convention ‘a being.’

“It’s only suffering that comes to be, Suffering that stands and falls away. Nothing but suffering comes to be, Nothing but suffering ceases.”

SN 5.10

In addition, SN 12.2 defines "jati" ("birth") & "marana" ("death") as applying to a "class/category" ("nikaya") of "beings". "Mother", "father", "sister", "son", etc, appear to be examples of classes of beings mentally created from attachment at "birth"; which are also subject to "death". MN 26 & SN 12.66 calls such things "acquisitions", which are subject to "birth" & "death" because they are "acquisitions" ("upadhi") the mind is bound to via "attachment" ("upadana").

Therefore, the above suttas appear to show 'saṁsāra' does not refer to 'transmigration' or 'reincarnation'.

As for the phrase: "The flow of tears you’ve shed while roaming and wandering is indeed more than the water in the four oceans"... literally it sounds ridiculous.

The quoted passage is similar in nature to the following.

"I", "you" and a view of a continuously existing self are used to generate the path, using this contemplation. Therefore, it's skillful means. It's typically targeted at those with self view.

“This noble disciple reflects thus: ‘I am not the only one who is the owner of one’s kamma, the heir of one’s kamma; who has kamma as one’s origin, kamma as one’s relative, kamma as one’s resort; who will be the heir of whatever kamma, good or bad, that one does. All beings that come and go, that pass away and undergo rebirth, are owners of their kamma, heirs of their kamma; all have kamma as their origin, kamma as their relative, kamma as their resort; all will be heirs of whatever kamma, good or bad, that they do.’ As he often reflects on this theme, the path is generated. He pursues this path, develops it, and cultivates it. As he does so, the fetters are entirely abandoned and the underlying tendencies are uprooted.
AN 5.57

I think that the "Eternalism" that's described as wrong view in DN 1 is like this:

The self and the world are eternal, barren, steadfast as a mountain peak, standing firm like a pillar. And though these beings roam and wander (through the round of existence), pass away and re-arise, yet the self and the world remain the same just like eternity itself.

... and this sutta isn't teaching that "The self and the world are eternal" so it's not teaching eternalism.

You emphasize the word "you" (as the subject of this question). I think there are other topics on this site, about how names and pronouns can be used "conventionally" without presupposing an atta -- that's also the subject of the "simile of the chariot" (in the Milinda Pañha).

Conversely, although there's no permanent "self", there are tears, suffering, in that dukkha is said to be an inherent characteristic.

I think it's important to read things in context, and not take things out of context -- the The Water-Snake Simile is an example of someone (Arittha) taking an element of doctrine out-of-context:

Regardless of how Arittha actually arrived at his position, the Commentary's suggestion makes an important point: that just because an idea can be logically inferred from the Dhamma does not mean that the idea is valid or useful.

Here I think the context is to point out that though the world and time are vast, so are the corresponding tears -- and seeing that ought to turn the audience toward dispassion.