The buddha is the only teacher of anatta

"The characteristics of impermanence and pain are made known with or without the arising of the Tathaagatas. The characteristic of no-self is not made known without the arising of the Enlightened Ones; it is made known only on the arising of the Enlightened Ones. For such wanderers and ascetics (taapasa) as the master Sarabha.nga are mighty and powerful and are able to express ‘the impermanent and the painful’: [but] they are unable to express ‘no-self’. For if they were able to express ‘no-self’ in a present assembly, there would be penetration of path and fruition in the present assembly. For the making known of the characteristic of no-self is not the province of anyone else; it is the province of the Fully Enlightened Ones only. Thus the characteristic of no-self is unobvious. That is why the Master, when teaching the characteristic of no-self, taught it by means of impermanence or by means of pain or by means of both impermanence and pain. But here it should be understood that he taught it by means of both impermanence and pain.

"But it is owing to not keeping in mind, owing to non-penetration of what and owing to concealment by what that these characteristics do not appear? Firstly the characteristic of impermanence does not appear owing to not keeping in mind, not penetrating rise and fall owing to its being concealed by continuity (santati). The characteristic of pain does not appear owing to not keeping in mind, not penetrating continuous oppression and owing to its being concealed by postures (iriyaapatha). The characteristic of no-self does not appear owing to not keeping in mind, not penetrating the resolution into the various elements (naanaadhaatuvinibbhoga) owing to its being concealed by compactness. But when continuity is dissected by laying hold of rise and fall, the characteristic of impermanence appears in accordance with its true essential nature. When postures are exposed (ugghaa.tita) by keeping in mind continual oppression, the characteristic of pain appears in accordance with its true essential nature. When resolving of the compact (ghanavinibbhoga) is effected by resolution into the various elements, the characteristic of no-self appears in accordance with its true essential nature.

"And here the following difference should be understood: impermanence and the characteristic of impermanence, pain and the characteristic of pain, no-self and the characteristic of no-self.

"Herein, the five aggregates (pa~ncakkhandha) are impermanent. Why? Because they rise and fall and change, or because of their absence having been. Rise and fall and change are the characteristic of impermanence, or the mode of alteration (aakaaravikaara) called absence after having been.

"But those same five aggregates are painful because of the words ‘what is impermanent is painful’ (S iv 1). Why? Because of continual oppression. The mode of being continually oppressed is the characteristic of pain.

"But those same aggregates are no-self because of the words ‘what is painful is no-self’(S iv 1). Why? Because there is no exercising power over them. The mode of insusceptibility to having power exercised over them is the characteristic of no-self.

“That is why the impermanent, the painful and the no-self are one thing and the characteristics of impermanence, pain, and no-self are another. For that which consists of the five aggregates, the twelve bases, the eighteen elements is all impermanent, painful and no-self; the modes of alteration of the kind aforesaid are the characteristics of impermanence, pain and no-self.”

the Sammohavinodanii (Vol. I, pp. 58-60):

"But what is taught by the Tathaagata in this Suttanta Division? The characteristic of no-self in the twelve bases. For the Fully Enlightened One, when teaching the characteristic of no-self, teaches it by means of the impermanent, or by means of suffering, or by means of [both] the impermanent and suffering.

"Herein, in the following sutta passage: ‘Should anyone assert that the eye is self, it would be untenable. The arising and passing away of the eye are obvious. But since its arising and passing away are obvious, he would thus have to conclude that ‘my self arises and passes away’, therefore it is untenable, … therefore the eye is no-self’ (M iii 282), he taught the characteristic of no-self by means of the impermanent.

"In the following sutta passage he taught the characteristic of no-self by means of suffering: 'Materiality, bhikkhus, is not the self. If materiality, bhikkhus, were the self, this materiality would not lead to sickness, and one would say of materiality: ‘Let my material form be thus; let my material form not be thus.’ But because, bhikkhus, materiality is not the self, therefore materiality leads to sickness and one cannot say of materiality: ‘Let my material form be thus; let my material form not be thus’ (S iii 67).

"In such passages as: ‘Materiality, bhikkhus, is impermanent; what is impermanent is painful, what is painful is not self; what is not self is not mine, that I am not, that is not my self’ (S iii 82), he taught the characteristic of no-self by means of both the impermanent and suffering.

“Why? Because of the obviousness of impermanence and suffering. For when a plate or a saucer or whatever it may be falls from the hand and breaks, they say: ‘Ah, impermanence,’ thus impermanence is obvious. But as regards the person (attabhaava), when boils and carbuncles and the like have sprung up, or when pierced by splinters and thorns, etc., they say: ‘Ah, the pain.’ Thus pain is obvious. The characteristic of no-self is unobvious, dark, unclear, difficult to penetrate, difficult to illustrate, difficult to make known…”