Defiantly 5, but if there's more than 15 words delete it?
That should clear out the walls of text and keep the "1 liner" screen shots.
You could also require text walls to be transcribed, no transcription = delete. If the poster can't be bothered to type it all out, why should we bother reading the jpeg distortion? (Again option #5).
One thing that stunk about reddit culture was the hyper-focus of the "meme/joke" communities. "Oh sorry your cat meme doesn't fit r/happycatmeme, it must be on r/cheerfulcatmemes", here's an account ban for your mistake."
Sure, we have a microblog community, but like someone else said, we don't need to go nuclear on people for posting here. Just tell them microblog exists. If they keep posting text here, baring any spam/malice, we can individually choose to block them.
"Ensign Kim, we hope you are readjusting well to life on Earth. We have been reviewing the reports and are finding you quite the accomplished Ensign, you were instrumental to the survival of voyager and her crew, even taking on captain duties at times. You were basically 6th or 7th in command right after the doctor. We feel continuing to call you Ensign Kim would be a disservice to all you have achieved in the past 7 years aboard Voyager.
Congratulations Super-Ensign Kim. You are dismissed."