A PC sat down to negotiate with an NPC in Sigil. The NPC attempted to read the PCs mind and find some specific tidbit of information.
The character, who had foreseen this and protected himself somewhat from this, has the Flaw of not being able to keep secrets very well.
I offered an XP to the PC if he let that information slip.
Another PC was meant to attend an extremely important meeting (Council Metting, TiA) along with his party. However he received an opportunity (the help of Elminster's ward) to covertly gain some valuable information from the personal library of someone (Elminster) attending that meeting. The information related to a topic his PC had an interest in. One of his Bonds is lore being more valuable than ABC. I offered him an XP if he skipped on the meeting (at great cost to his party) to lean into his Bond and use the opportunity to acquire lore from Elminster's library.
A PC had a Bond that considered a certain NPC (previously a PC) his brother and would do anything for him. Well that NPC was caught in a city being pulled into Avernus (Elturel, DiA).
He purposefully split from the party to attempt rescue this NPC earning himself an XP.
I'm essentially running 2 campaigns now (1 the main group and 1 for him, separate sessions).
These are just a few examples of how we leverage the TIBFs to truly test the core of the character. Player has full control over the decision to lean into their TIBFs or not.