Maybe "kender ace" as racial trait could be useful for a feytouched subrace, but it is not coherent with the standard or "classic" kender.
Kender Ace (or a beefed up version of it) is exactly the sort of thing that should be made into a racial feat, imho. Give people who want to lean hard into the whole Tasselhof thing a way of doing so, but without shoving every other kender PC in the same direction.
The defining trait of kender should be
curiosity in my opinion. Allied with the fearlessness that turns that curiosity into something that gets them into trouble all the damn time. That leaves plenty of room for non- thief kender. That sort of character of course can exist, but they’re not the be-all and end-all. Curious kender can be in-theme, and consistent with the lore, without being jerks. The curiosity doesn’t always have to be aimed at the contents of your friends’ wallets. I’d like to see an archaeologist/historian lender who is FASCINATED by pre-cataclysm krynn and desperately wants to ask Soth a whole bunch of questions about it, cos he was there. Or a beastmaster ranger kender entranced by the insect world, whose beast companion is a giant ant, and who enthusiastically points out the cool anatomical adaptations of his slavering, venom-dripping best friend to strangers at every opportunity, no matter how hard they try to change the subject.
You can do ‘childlike innocent curiosity’ in a number of ways that doesn’t involve wandering off with people’s precious heirlooms, is what I’m saying.
Having said all that, while I like the way it’s been done, this version of the kender seems to be very much mechanically weaker than, for instance, any phb halfling subrace. While fear immunity is a bigger deal in a dragonlance campaign where dragonfear is going to be flying all over the place, I still don’t think it quite measures up. Another minor feature might be in order too, I think.