> greater potential or likelihood of abuse or any degree of taking advantage of people.

It seems like this is the core of the disagreement. The factors here are complex, but here are some things I would point to as a starting point:

- You often have large financial differences that can start completely accidental power imbalances in otherwise healthy relationships if not managed closely. This can happen regardless of age, but age/life stage will introduce this risk more often. Is it a hard and fast rule? No. Is it a "greater potential or likelihood"? Absolutely. Apply that test to the later things as well as well.

- Housing. What happens when only one person's place is a viable place to stay the night? Again, this happens outside of age related gaps, but happens more often with them. See dorms and roommate situation mismatches. In that 18 year old high schooler situation above, literally parents.

- Brain development. We don't reach full cognitive decision making maturity until we are 25 IIRC. This can literally shape decisions and their framing within the relationship and create a vector for abuse. To be clear, this does not discount people's cognitive ability under 25 at an individual level but is a subtle statistical risk factor.

- I would not be surprised to find statistically that people who date beyond these "considered widely acceptable" boundaries are more prone to these types of manipulations and abuse, and generally more unhealthy relationships + lack of relationship experience. Anecdotally I've certainly found it to be true, but I'm not trying to claim that as data here beyond a single point. It's something that would need research and likely study.

- Whether you think they are fair or not, the social effects are real in today's world. I've seen this personally act as a "multiplier" on existing issues. (There's a better way to approach this as a society, but it's not to ignore the potential risks here entirely.)

- Even when fairly treated socially, social circles can not mix for reasons around age/life stage gaps without any bad assumptions. The lack of mixing friends and circles IMO is a fair place to assume potential power imbalance issues, again when combined with logistics on housing and finances. It's an easy way to harder shift the balance of life sharing in one direction, often the person farther along in life.

If you're reading all these and saying "I know relationships that have all these issues without an age gap" then great, they/caring friends should probably do a self-check on those as well! But it doesn't mean that we should ignore how these gaps can be a statistical risk factor for bad relationship dynamics.

If you think all of these aren't real, I'm sure others can come up with things that fit the bill. Proving the complete lack of statistical likelihood is a tough case to begin with, and there are just so many factors here that I can't imagine any study confirming your argument here.

> But, to be frank, is there anything more to it than the ick factor?

FWIW, ick factor is not a part of it for me at all, or I would have no issue dating a 21 year old college undergrad myself on that test alone.

Even further though, I would argue many people's "ick" is derived from some less reasoned through logic in the same vein as above. It's a subconscious smell test people should absolutely examine, but shouldn't be written off completely as it does come from somewhere. People just need to examine the source better.

> I'm just against the casualness of assuming there's any good reason for this concern

I can totally agree here, but there's a middle ground. Think of it as checking for prostate cancer when you get older. Should a doctor just assume you have cancer? Absolutely not. Should they check regularly for it, more often than with someone younger? Absolutely they should.

I think what may be happening is you're over-applying my original post. I'm not prescribing any ostracization for these red flags, but rather reflection and awareness of potential issues.

PS: At a personal level, I avoid these flags entirely because I have plentiful options without these flags. Why take the risk? But I don't persecribe that in the same way to others, I just pay closer attention if it is someone I am close enough with to care about and the reflection/analysis/opinion is wanted by my friend.