That is soke nasty looking code. Chances are it came from a conversion of an old Mobi. The code in old Mobi can be that nasty.
It could be slower to render, but on most modern Readers such as your T2, you won't notice it.
Personally, I'd give the code a good going over to get rid of all that garbage and redo the CSS so it matches what is supposed to happen. It's not that difficult if you can make use of search/replace/regex to get rid of the unwanted code.
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