Hard to say. From a pure emotional viewpoint I think that paying several times a month looks fishy. Is the cardholder stretched and working on a cash basis and feels he/she has to pay when they have the money lest they spend it on something else? In the end it makes no diffference, but no one knows how AMEX's internal systems view multiple payments. There can be reasons (I guess) for someone wanting to do this, but anything out of the norm always sticks out. I doubt more than a couple of percent of cardholders make multiple payments during the month, so it is easy for AMEX to target these accounts to see 'wassup'. Perhaps their studies have shown more problems in these accounts, or not.
When in doubt I tend to act like the crowd unless you want to stand out. When it comes to using credit I never want to stick out.
For AMEX to think that early payments or chunk-based paying is bad, they probably would have some actuarial data that shows people who generally don't pay by AMEX's given pay date and pay erratically early have a tendency to default more than people who just auto-pay and forget about it.
That's a mixed bag . It could very well be true that people who make multiple payments in a month do pay their bills erratically, including making late payments or defaulting. It could also very well depend on the debt size more than anything.
IMO, if you "pay in chunks" the best way to do this is on a schedule, say every 2 weeks or 10 days. This represents a schedule of cashflow and an ability to pay. If your payments are sporadic and random, this is harder to get it patterned and recognized within any trend.
If you pay every 10 days (1st, 11th, 21st) and pay the current outstanding charges, this will provide an easily recognized pattern.
If you pay on the 1st and 15th, this also is easy to recognize. It looks like "paying the bills" with you pay checks or cash flow.
IMO, AMEX likes to see patterns and trends. They do not like haphazard or sporadic, because they can't get a fix on you. So, whether charging or paying, you are being analyzed, so try to be predictable where you can.