To summarize the thread:
Former D1 really isn't a very useful term for describing your running ability, although it may have some relevance to your collegiate track experience generally in that it is some indicator that you would probably face a generally higher degree of competition at conference meets.
On the average D1 schools are going to have better track and cross country teams than D2 or D3 schools.
The better D2 and D3 teams are probably as good as or better than a middling D1 team, but are not in the same ball park as above average D1 teams.
The all time best D3 runners (the Lameres and the Dan Maiers of the world (Lamere before Lamere was Lamere), which are limited in number) would be competitive in conference meets at even the better D1 conference meets, and the D3 All America types would probably be able to make most D1 travel teams and some would score points at most, but not all, D1 conference meets. But as a general matter, the quality, and particularly the depth, on a D3 team is significantly inferior to the quality and depth of D1 teams. Same for the D2 guys.
If you want to use D1 as a descriptor of your running ability, it would be more useful if you also added something like "former scorer at my D1 conference meet" or "former D1 regionals qualifier" or "former D1 athletic scholarship runner" because absent a description of that nature, the D1 qualifier in and of itself is not meaningful.
Those who get worked up about guys who describe themselves as "former D1" may have a factual basis for that irritation, but may be expressing that irritation as a result of some sort of "little brother" complex.
Those who refer to "baby nats" or generally deride the lower divisions are more often than not going to be marginal D1 guys who are overcompensating for their mediocrity and need to try to degrade others to feel better about their mediocrity.
Did I miss anything?