I know you mentioned this in another thread. Did you follow up with Tesla to see if there was an option in the contract to explicitly limit your sale to 15 years? I still think that Tesla essentially has two boilerplate sections for their contracts - one that says "Tesla owns the RECs" and one that says "customer owns the RECs." I suspect they haven't really contemplated the issues in IL.
And it seems like IL is a fairly unique market in that you sell a 15-year block of credits, where other states with REC-style systems you sell them as you go. Additionally, it does not appear that there is much or any marketplace as a consumer to sell the credits - you pretty much need to get the money from your installer or the broker your installer uses. I feel like the way the system is setup in IL tends to lock you in to what the installer wants to offer, regardless of what installer you choose, so my question is whether what Tesla is offering for the ABP is similar to other installers. If it is a lot lower, definitely worth complaining to Tesla. If it is similar, complaints might be better directed at the state agency.
The overall answer to your question is that on this forum, most people are probably not okay with it and that is why they decline that option. But they have access to a marketplace to sell the credits themselves, which it seems IL does not, at least at this time. And for those who do accept it, they understand the nature of the transaction.
All that said, what will the market for those RECs be in 15 years in IL? In MD, I know they are set to decline, and I would not be shocked in general if the entire concept of RECs looks totally different in 15 years - though it will probably depend a lot on how quickly the ongoing transition to renewables actually happens. RECs only make sense to encourage the transition to renewable energy, as I see it.