It's very easy, if you are really ILE: an SEI will listen endlessly to your theoretical Ne-ramblings, and give you the impression they understand and agree, even when they don't. Your ramblings will be met with disapproval by ESIs, and at best they will argue with you and constantly disagree with most of what you say, opposing it with their own perspective, which you think is rather narrow-minded, outdated and makes you feel they haven't understood a single bit of what you said, that they didn't get the point.
ETA: another thing, SEIs, although not as expressive as ESEs, might laugh boisterous when they think something is very funny. ESIs are more likely to chuckle, or just smile, not even baring their teeth.