It's not a blockchain in the sense that there isn't any consensus mechanism. But there are lots of copies of the data. This is more a function of what relays you connect to at this point though since there are only a few gossip implementations that actively try and spread your data to more relays.

Since events are just JSON they can hold ANY amount of text. Check out https://habla.news. It's a blogging platform on #nostr and deals mostly in type 30023 events (long-form content).