IIANM, in the local majority language, it has been Myanma since independence -- as in "Pyidaungzu Myanma Naingngandaw", i.e. the Union of Myanmar. But, in the international "community" it was referred to as "Burma", the official name from British colonialism. Not dissimilar to "Nihon/Japan", "Zhongguo/China", "Deutschland/Germany". I think in the parlance it's local vs. conventional name.
The SLORC promoted Myanmar as the conventional name for international use, as also "Yangon" instead of "Rangoon".
So, in Burma itself, I don't think there's any big deal. Speaking Burmese, it would be Myanma Naingnandaw. But it's to do with the relationship of the international "community" to the political groupings in Burma/Myanmar, and taken as a touchstone of the relationship to the regime.
As for trade sanctions on Burma -- can it really have any impact? I think S Africa was an exceptional case because of the major involvement of the international economy. But Burma?
kj