If someone reads these posts correctly, they may tend to believe it is a normal occurrence. But do you really believe everything you read?
Soooooo.........you suggest it's not normal and yet do not offer any answers as to what might be the cause??? The purpose of these forums is to ask questions of our fellow riders in the hopes of getting answers to your questions. I don't believe everything I read, but if 99% of the replies point to the same answer or suggestion, then I guess it is a pretty safe bet to go with it (unless of course, someone such as yourself comes along with a different/better? answer to look into).
Every Harley I've had has made those sounds when it started cooling off. Primarily from the exhaust/heat sheilds.
It's not just a Harley thing.
Every internal combustion engine with an exhaust system will do it.
As different metals heat and cool, they expand/contract at different rates.
The "tink...tink...tink" sound you hear is caused by the cooling (contracting) process.
Pull your car or truck into the garage where it is quiet, and you'll hear the exhaust system on them doing the same thing.