It's things like a swimming pool or rec room for an apartment complex. No individual apartment could possibly fit or afford a pool or a billiards table, but if every condo pays five dollars a month toward maintenance of such amenities then everyone gets to enjoy them.

There are some circumstances where a HOA is important. If you're living in a condo complex, for example, you need a HOA to gather the money to repair collective property.

It's insane for nearly anything that doesn't revolve around collective property, though.

The "of course" is an interjection modifying the first clause of the sentence. I can put it more or less wherever I want. The base sentence is "This is ridiculous, hence why it's funny", with "of course" being inserted as flavour - "Of course, this is ridiculous" and "This is ridiculous, of course" are equally valid.

Anyone who tells you that there is exactly one correct right way to write English is a filthy liar and not to be trusted. English exists to play with.

I genuinely don't know what you're asking.

It's a linguistics joke. "Polyamory" is an English word constructed out of a Greek prefix ("Poly", meaning "many") and a Latin suffix ("Amor", meaning "love"). They're saying it's a hideous Frankenstein word and should be replaced with "Polyerosy" (all Greek) or "Multiamory" (all Latin) instead.

This is, of course, ridiculous, hence why it's funny.