There is little to no evidence supporting the claim that regular tongue scraping improves anything except bad breath and oral hygiene; however, very little research has been done to credit or discredit such treatment.
Let's examine the talking point in her article, 5 Reasons Why Everyone Needs A Tongue Scraper:
You want to boost your immunity.
Notice there is no citation in the entire article for this and there
is no URL provided within her claim, unlike the bad breath commentary.
You'd like to improve your digestive health.
The URL she provided for help with digestion has
nothing to do with digestion, merely for taste and periodontal
There is no evidence within her own article, that would lead one to believe that scraping your tongue would do anything but fight off bad breath. Her simply stating that it does is mere conjecture, however she is a scholar in an accredited university and may yet provide the necessary peer reviewed research to back up her claim.
Alternative medicine practitioners consider this toxin-removing-tongue-scraping as a part of Ayurveda Treatment. In the U.S., Ayurveda is considered a form of complementary and alternative medicine (CAM).
Note: Don't dismiss alternative or holistic treatment if it is indeed proven effective. There are just very little peer reviewed research into those forms of treatments; take them at face value. Some of our greatest discoveries were by those alternative measures and 'accidents' after-all (credit: Sklivvz)
The Mayo Clinic only talks about temporarily relieving the effects of bad breath with tongue scraping [as a treatment]; there is no mention of removing toxins at all.
The Journal of Applied Oral Science1 doesn't mention any reductions of toxin absorption - in fact doesn't mention the word toxins at all - only microbial reduction related to bad breath.
Asikainen S, Lai CH, Alaluusua S, Slots J. Distribution of Actinobacillus. actinomycetemcomitans serotypes in periodontal health and disease. Oral Microbiol Immunol. 1991;6(2):115-8.