Hi Andrij, I can sense a bit of misunderstanding here.
Noone is blocking WLM participants; it happens so that the e-mail address used by the person that contacted you was globally as part of a wider range block. The block was performed by Vituzzu on September 4, and also extended until 14:46 (UC) on September 19.
This block--as mentioned earlier by Federico--does not prevent account creations (I double-checked that), but it might be some kind of an error if the user cannot create an account on Commons.
In any case, I can create an account for her/him; please send me the details (desired login and e-mail address) /off-list/ and I will create the account as soon as possible.
-- Tomasz W. Kozłowski a.k.a. [[user:odder]]