In magento1 the remove tag was global and once a block was removed it could never be added back in:
<remove name="catalog.compare.sidebar" />
Is the same true in magento2?
<referenceBlock name="catalog.compare.sidebar" remove="true" />
It isn't a simple yes or no answer unfortunately. From looking at the remove section in the dev docs it sounds like you can easily remove and 'unremove' blocks with
Now I say this isn't a simple answer as the functionality doesn't seem to work, or not always as expected anyway. Quite a few people have noted that if a block has been removed in a parent theme, then setting
remove="false" does nothing - taken from this Github issue.
So until that issue has been resolved I would say yes it is the same as Magento one, once a block has been removed it cannot be added back.