Answer

Eating bread in the marketplace is a matter of social norms. When people sit at tables on the sidewalk and eat, that is very accepted, and I see no problem with it. In a place where this is not accepted, it is forbidden to put oneself into a degrading situation (although there is no explicit source or warning for this in the Torah). And indeed, degraded people are also disqualified from testimony. See, for example, Shulchan Arukh, Choshen Mishpat 34:17-18:
17.
One who is versed neither in Scripture nor in Mishnah nor in proper conduct is presumed wicked and is disqualified from testimony by rabbinic law. Therefore, testimony is not entrusted to an ignoramus, and testimony is not accepted from him, unless he has been established as one who occupies himself with commandments and acts of kindness and follows the ways of upright people and has proper conduct, even though he is an ignoramus and is versed neither in Scripture nor in Mishnah. Thus you find: every Torah scholar is presumed fit unless disqualified. And every ignoramus is presumed disqualified unless it is established that he follows the ways of upright people. And anyone who accepts the testimony of an ignoramus before he has this presumption, or before witnesses come and testify that he conducts himself with commandments and proper conduct, is an ignoramus himself and will ultimately be held accountable, for he causes the loss of the property of the Jewish people on the basis of wicked people (Tur in the name of Maimonides).
18.
The degraded are disqualified from testimony by rabbinic law; these are people who go about eating in the marketplace in front of everyone, or those who go about naked in the marketplace while engaged in some degrading labor, and the like—people who are not concerned about shame. All such people are regarded like dogs and are not careful about false testimony. Included among these are those who publicly accept charity from idol-worshippers, even though it would be possible for them to support themselves privately; they degrade themselves and are unconcerned. All such people are disqualified by rabbinic law.
As for the prohibition on putting oneself into a state of disqualification from testimony, that requires discussion. Is it forbidden to get married and thereby become disqualified from testifying regarding one’s wife’s relatives? Obviously it is forbidden to commit transgressions, but not because of the disqualification from testimony. That is only a consequence. Still, there is an obligation to testify, so one could argue that putting oneself into a state of disqualification from testimony involves a prohibition because one is placing oneself in a situation of compulsion that prevents one from performing a commandment.
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Questioner:
Why is there a prohibition against degrading oneself (you wrote that there is no source for it)? There also seems to be no reason to prohibit self-degradation, because someone who degrades himself anyway will presumably not listen to such prohibitions. Beyond that, I remember stories about people from the Mussar movement who would deliberately degrade themselves in order to break the trait of pride—was that forbidden? Also, would it be correct to say that anyone who degrades himself is disqualified from testimony? Or is this only an indication that he is not careful about falsehood, but in a case where there is a justification for the self-degradation, perhaps we would say that he is not disqualified from testimony?
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Rabbi:
I wrote that I do not know the source, but Maimonides (Commentary on the Mishnah, beginning of chapter 3 of Sanhedrin) seems to imply that there is such a prohibition, apparently as a matter of proper conduct. The Novardok stories (asking for nails in a pharmacy) are indeed problematic, and on the face of it it is forbidden to do that (also because of desecration of God’s name—what will people say about yeshiva students?). Sometimes, however, repentance can justify a prohibition. See Sefat Emet on Maimonides’ words: “Who is a complete penitent? One who returns to the same situation, while it is in his power, and does not transgress.” Sefat Emet infers that although it is forbidden for a person to put himself into a situation where he may be drawn to sin, if this is needed for repentance then it is permitted. His inference is not compelling, however, and this is not the place to elaborate. Perhaps Novardok relied on such an approach.
The question whether someone who degrades himself is disqualified as an inherent personal disqualification or because of suspicion of lying needs analysis (I do not recall a clear proof at the moment. Usually this is examined in light of the question whether such testimony is accepted in the testimony of a woman to permit her from being an agunah, where they accept anyone who is not suspected of lying. One would have to check whether this is discussed). On the face of it, it does not seem to be about suspicion of lying. Why think that someone who degrades himself is unconcerned about lying, like a wicked person motivated by theft? It seems more that he is like an ordinary wicked person (though certainly he is not liable for lashes and does not fall under the Torah-level category of a wicked person disqualified by Torah law. His disqualification is apparently rabbinic. That is another indication that this is not about suspicion of lying). He is also brought in the context of the Talmudic passage dealing with wicked people. So a justification would not help (and the practical difference would be whether Novardok students are disqualified from testimony).
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Questioner:
From the wording of the Shulchan Arukh that you cited above, it sounds like it is saying that the very fact that they are not concerned about shame is a clear sign that they are also not concerned about false testimony (“The degraded are disqualified from testimony by rabbinic law; these are people who go about eating in the marketplace in front of everyone… people who are not concerned about shame. All such people are regarded like dogs and are not careful about false testimony”).
There is also logic to such a claim, since people refrain from giving false testimony partly because if they give false testimony and are caught, it will bring them great shame, and that deters them from lying. But someone who cares less about being degraded will be less deterred by the disgrace involved in false testimony.
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Rabbi:
Correct. So what is the question?
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Questioner:
If so, then where there is a justification for the self-degradation, and generally speaking that person, were it not for the justification, would avoid degrading himself, it would seem that we cannot say of such a person that he is suspected of lying. Therefore Novardok students would be fit for testimony (unlike what you said earlier).
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Rabbi:
Indeed, if the self-degradation is the basis for suspicion of lying, then it is reasonable that in the case of Novardok that would not apply.