Hardly anyone on a DTV faces any issues coming and going. As long as you don't overstay your 6 month (180 day) stamp or if you've extended it, your extension, which gives you an additional 180 days, then you're fine.
While not required, it does look better to immigration if you're coming and going regularly, let's say, spending 1 or 2 months in the country leaving for 3 or 5 days, coming back for 2 weeks, leaving against for a week, coming for 4 months then departing for 3 weeks that sort of thing, rather than spending 180 days, doing a same day land or air border run and then returning.
However, I have generally not heard of anyone facing trouble for doing that on a DTV just that it's best not to do it more than once. Look like someone who has a reason to travel, on business or for pleasure (or both) and immigration will just wave you through.
I very much doubt people are having their accounts closed. Not being able to open one, sure, that's not surprising, but unless you're a scammer or have used your account for nefarious purposes, it's very unlikely to be taken from you.
Aside from some Burmese DTV holders, pretty much everyone else has no issue with entering and exiting whatsoever. It's almost guaranteed unlike if you're on a visa exemption or tourist visa. The DTV is a good visa to have, except for the difficulties with banking (which will hopefully change once the current crackdowns come to an end).
You clearly have no idea how Thailand operates. There is no consistency. Whereas a tourist visa holder may find it next to impossible to open a bank account, a DTV holder might have a different experience.
What you're saying is nonsense. It's up to the branch and each individual you ask will say something different based on what they believe to be correct. Nothing to do with "saving face". What a nonsensical assumption on your part.
Cars not in your name can be taken to Laos as well with a letter of authorization. However, generally, rental car companies won't issue this letter (in rare cases they might). You can also self-drive a rental car in Laos, visit Avis. I know the general manager and founder of the company. Their cars are allowed to be driven into Thailand.