Is there any respectable Rabbi in the modern Orthodox Community who holds that it’s not so bad if a married lady does not cover her hair?

Shalom, Thank you for your question. To the best of my knowledge, all Rabbis agree that the halacha requires married women to cover their hair. There are many varied opinions of how, and how much, the hair should be covered. [I should perhaps be careful with the word “all” - as there was one Rabbi (not Modern Orthodox) who ruled that in his time married women did not need to cover their hair (Rav Yosef Messas, d. 1974). However, it is possible that even according to his arguments, today, when it is very widespread that married women do in fact cover their hair, he would rule that this is obligatory. Also, his ruling has been objected to by many]. Your question uses an interesting phrase, “it's not so bad”, which is worth taking note of. There have been several Rabbinic articles written to discuss the phenomena of married women who do not cover their hair. And while they agree that married women do need to cover their hair, they look for “limud zchut” - that is a way perhaps justifying, even in part, behavior that halacha does not approve of. These articles are trying to come to a point where the phrase you use - “it's not so bad” - would apply. That is, if we ask these Rabbis what is the proper halachic practice, they will say clearly that the halacha is that a married woman should cover her hair. However, in order to try to justify the reality of women who do not follow the halacha, they go to lengths to find sources that, while not accepted as the halachic norm, nor halachic ruling, could be used, perhaps using your phrase, to say that it is “not so bad”. (The most extensive of such articles is that of Rabbi M J Broyde, found in a special supplement to the Tradition journal, called “Hair covering and Jewish Law: Biblical and Objective, or Rabbinic and Subjective”. It can be found online.) I should point out, that major Rabbis (including my own Rav, Rabbi Y H Henkin) argue very strongly against the reasoning outlined in such articles, and rule clearly that there is no halachic justification for uncovering of the hair. That would certainly be the overwhelming understanding of the Rabbinic world, including those in the Modern Orthodox world. To sum up – a married women needs to cover her hair. There are Rabbis who attempt to find ways to lessen the sin of those who do not follow this ruling, by finding sources and reasoning that would be able to justify such behavior. Even they would agree that the normative halachic ruling obligates hair covering. Blessings.