Clarifier won't have any long term impact on a DE filter. They can sometimes lead to a day of frequent bumping/backwashing, but the water clears up quickly, the bumping/backwashing ends, and everything is fine again.
Clarifier causes small particles, ones so small that they pass right through the filter, to clump together into larger particles which the filter can trap. If you are in a situation where clarifier is required (very rare by the way) then adding clarifier would result in a sudden and large increase in the amount of stuff that the DE filter catches. In some cases that could lead to a very frequent need to bump/backwash the DE filter for several hours to a day, as it suddenly becomes able to filter out the newly clumped together particles. Once that period ends everything is back to normal with no damage done.