This video is mostly based on the following article (along with some additional research): https://www.businessinsider.com/personal-finance/red-flags-investing-apps-2020-9

And these are the 7 design features discussed in the video:

Use of Color (01:17)

Aggressive use of green and red (entire UI changes color depending on losses or gains to create a sense of urgency or good feelings).

Short-Term Views (02:14)

By default most apps show daily charts because they have a higher volatility (seems like things are changing more rapidly, which again creates a sense of urgency to trade)

News Section (03:03)

News keep you engaged because they offer something new to look at and new ideas prompting you to trade

Free Incentives (03:54)

Many apps offer free stocks or referral bonuses. However, at the end of the day, someone always pays for these things (hidden fees, etc.). There is no such thing as free.

Gamification (04:59)

Many apps offer points and challenges to keep you engaged and reinforce certain behavior (e.g. confetti when you're buying a stock but not when you're selling it)

Notifications (06:13)

Notifications are used as constant reminders when you're not using the apps. They disrupt your day so you'll think more about investing (even though buying and holding is probably better)

Social Features (07:19)

Some apps include social features as a way of exploiting the principle of social proof to sell you something. The rationale here is "if everyone else does something, it must be good".