So earlier today I posted a question about why I couldn't use my Marauder's Map and some answers said that if I had the invisibility cloak option on in my settings, I wouldn't be able to use it. Now while this answered my question (I looked in my settings, and sure enough, the invisibility cloak option had been turned on), it brought up another question for me. What would be the point in buying the invisibility cloak from the Weasley's Wizard Wheezes if the description said that we could use it to hide from the Marauder's Map, something that we can do without even owning the product? If someone bought it, would the whole point of the cloak being in their inventory be that they can use it in character and if needed, prove that they actually own the product?

TL;DR Does the Invisibility Cloak from the Weasley's Wizard Wheezes have a use or is it just there for IC flavor?

It used to have a use but doesn't any more. It also doesn't have an IC flavour I think since it would be a pain to moderate. You could possibly use it in unmoderated threads though, but it wouldn't work perfectly.

Lucia's right, it used to have the OOC site function of hiding your presence on the map and also hiding your last online date on your profile, but Zach decided that privacy should be available to everyone, so it was made a setting instead.

The cloak can now be used IC but the charms would wear off from time to time and would need to be reapplied: It's not flawless, there will be a chance of discovery and you cannot stay invisible indefinitely. It can be brought into moderated threads but only with express permission by the moderator, and they would decide whether people notice you and how long the invisibility effect lasts.