Not sure about Jesus, maybe he just made a status move against his competitors, but in general...

Goodhart's Law applies to bragging about donations too -- if you make it a norm, people will optimize for visibility instead of doing good; there will be charities helping them to optimize for this goal... and soon you may get a culture where people donate a lot to charities that actually don't do much good, because most of their spending goes on increasing the visibility somehow.

Taking a wider view, maybe we would agree that maximizing donations to EA is still a positive goal, even if it brings some negative side-effects. But remember that most people don't care about effective altruism, and would consider other charities more worthy. So you might be effectively creating a culture where people get points for publicly donating to organizations that you might find useless or even harmful. (Imagine organizations for effectively spreading a religion, or effectively spreading a totally mindkilled version of a political movement you disagree with.) Now you would be stuck in a situation where you either have to "voluntary donate" money to a cause you hate, or become a visible defector because everyone else around you already made their donations public.