I've collected
Pros, Cons and Other thoughts on Tipping micropayments on the forum a while ago. As much as I'd like to have the feature, I don't think there's much demand for it.
LN is probably unsuitable for tips since the recipient has to be online. That's why these LN tipbots all hold your money, which I'm not a fan of. If you're using LN through a trusted third party, then you're better off not using it at all.
For small amounts, I wouldn't mind using and trusting a third party for low-cost transactions. Exchanges currently hold much more funds.