Yes, I did a test using a confirmed transaction and they still gave me the "Submissions are beyond limit. Please try later." message, even though they used to give "Transaction already confirmed" message for such transactions. Then I tried clicking the Paid service button (I have an account there) and this time, it gave the "Transaction already confirmed" message.

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So it's safe to say, ViaBTC's free transaction accelerator is indeed switched "OFF" for the time being. Whenever someone has similar results, just stop bothering trying their free services (their paid services are working though).