It would be nice if there was a button you could click in cataloging that would go through the marc record and add all the necessary punctuation in - other systems have such a feature, it has been done, but in Koha you have to know the punctuation rules and enter it by hand.
This would be an amazing feature, but is not easy to do. We have written a converter to add punctuation and have found that the LOC documentation often is not clear on what should be used or there appear to be different options.
I think if one can add the punctuations automatically, the idea would be more to keep the records _clear_ of it and add it only when rendering the display in OPAC or the like. Having these chars around usually only causes headache e.g. in exports to structured formats, transformation etc. BTW: AFAIK the German union catalogue GVK / K10plus proceeds this way. No chars in the record, add them once needed. (Though they start out from PICA+ internally.)