Do ld submissions hurt your sites?
 

Do linkdump submissions help or hurt your sites search engine listings?

Google still shows a few backlinks from link dumps I haven't submitted to for months, so while I can't say for sure I'd be inclined to say "no" :)

It should not hurt your SE listings, beacause you have no control over it. If if would be possible to hurt your SE position this way, then it would be very easy to kill your competitors. But this is just a grey theory, actually I think that you can be temporary hit by "too much backlinks too fast" filter, but for a long run any backlink is helpful.