The inflation rate over time will actually tend to zero, since each additional 5bn coins represents a smaller proportion of the total amount. A constant quantity over time translates into a decreasing rate of inflation.

That's not accounting for lost coins (either because the wallet is lost or the owner is prevented from spending them).

The idea in the github thread seems to be that the 5% inflation should approximately cancel out the unknown loss of coins that would be going on.

That's also insufficient over the long term since coins are lost as a proportion of the total per unit of time.

This is important - anything that a majority of a cryptocurrencies userbase doesn't like won't get implemented because they wouldn't upgrade the protocol, they would fork it.