I think this is rather weak and mostly arguing against a straw-man. I don't see Effective Altruists arguing that you should refrain from investments in your human capital. It makes sense to cut down on consumption (eg. eat out less). But I don't know of any EAs arguing that you should refrain from say buying books.

The article implores us, instead of donating large amounts, to "make yourself a better, smarter, friendlier, and more capable person. Buy books. Take classes. Get a better job. Move to a better city. Throw parties. Get a gym membership. Go out dancing. Travel places you haven’t been. Build things you haven’t built. Start a business. Learn a craft."

But lots of these things don't actually require money, and those which do require money don't require much money, so we can still have plenty left to donate. So I find the piece unconvincing.

It's worth reading the comments of that original post if you haven't already. I think some of what the author suggests is pretty standard 80k hours/GWWC advice - invest in your human capital, donate small amounts to keep the habit, while you are poor/earning little (maybe it wasn't at the time that was written though).

One thing he doesn't really touch on is the time value of money - it's worth more now than it is later - both to you and to the charity you choose to donate too. You may not be rich in 40 years if you donate your spare money now, but the effects of that money could be just as great or greater spread out over the recipients. Right now, according to Givewell, Malaria Consortium saves the equivalent of a life for around $2500. That is likely to go up and may be vastly more in 40 years.

I think most people agree though that you shouldn't donate more than you can afford. If you put yourself at financial risk, or live in a way that constrains your job prospects or results in burnout, you're hurting both yourself and the causes you support.