I replied to you you elsewhere in this thread, but they never claimed to be getting 28% CTR. They only claimed that this format performs 28% better than alternatives.
If a different ad format was getting 1% CTR, then a 28% improvement is still only a total 1.28% CTR.
What’s more likely, someone at reddit fucked up an analysis, or these ads are 14x better than Google or 31x better than FB?
What's most likely is that you misread or misinterpreted what was stated. It says the new format outperforms other types of ads by 28%, not that they get 28% CTR.
I mean, generally I'm all for shitting on reddit, but there's also a third option: Reader's not understanding what 28% better than other ad types means.