I know this was a good laugh when I read it years ago, how some people would only put their certs in their email signatures if someone else did, just to out-do their show off stuff.
I personally know of someone who puts things like "Mensa Representative" and such in their email signature (even on internal emails), I assume just to stroke their own ego about how great they are.
I use them only on external emails where I have to make an authoritative to a customer or vendor, to kind of puff my chest showing I've been there and done that, otherwise I leave them off most emails I send.
How about you ladies and gentlemen?

EDIT:
I should clarify, I only put the mini-logos underneath my company name, as the 4 cert logos listed fit it perfectly and the
Meraki green symbol at the end looks pretty damn cool when sending external emails