Now, I own and am also in contact with many successful pages in Instagram, most who use Comments for 1 reason,
Leaving it in the Caption Results in the good old "Read More" now this can be different in different categories such as Articles and News Related things, but as for something with a small caption such as "Good Morning" than spacing and hashtags results in the "Read More" which isn't signature to peoples desires which results in many different behaviors such as effects on Credibility, Hate, UnFollows.
I have done most, In comments it gets saturated so people won't be able to find them so it's undetected basically unless someone intentionally looks for it.
I've done my research, I've spent many hours on Instagram, Many years to be exact, With many other mentors, business partners and friends.
This has been specifically something I've looked into and with tests with many accounts ranging from 0-500k Followers, and all of the Data came back that using Caption Hashtags resulted in drops of followers (Not Much) but just some, People leaving comments about the hashtags.
And don't worry I don't feel disrespected, I know I am credible, I know I have credible sources and I am confident in my years of knowledge from growing accounts in Instagram
Thanks!