With negative rates, the banking model is undermined. They should not make up for themselves by bludgeoning their most vulnerable customers with 24 euros for a simple "newsletter".

Bank charges and payment incidents: Banks are accused of targeting their most vulnerable customers.

Have the banks changed their model? In the old days, they paid themselves by making our money work. But now, with negative rates, money is no longer yielding anything. Banks must therefore remunerate themselves otherwise. How are they doing? They charge their customers, it is the famous bank charges that have exploded in recent years.
The typical example is the account maintenance fee (you must now pay to be a customer). These account maintenance fees did not exist almost ten years ago, they have now become the rule and are billed around 19 euros a year.
Even if, this year, the tariffs remained overall wise as shown by the latest report of the Observatory of Fiscal Rates. In 2019, banks met their commitment not to (or little) increase their rates with the yellow vests crisis.

But the situation may not last. Above all, we observe a great disparity from one bank to another?

This is very true, in terms of payment incident. When your account switches to red for example, the bank sends you an alert mail that can be charged between zero and 24 euros. This is the case for all payment incidents and up to 182 euros, for example, for a banking ban.
Hence this concern of Finance Commission members who are wondering whether the new banking model is not simply about bludgeoning the most vulnerable customers. It is estimated that there are about three million so-called "fragile" customers in France. How many billions are reporting these three million fragile customers? This is a real question because we should not find ourselves in what MP Chassaing calls in the Voices "a system of reverse solidarity" where the incident costs charged to the poorest would be used to finance the free services offered to the richest. It would be a little Robin Hood upside down and that would be pretty shocking.