有難くも、10000hit越えのお祝いイラストを頂いてしまいました！本当にかたじけないです。

、！。

I'm so grateful — someone actually made a congratulatory illustration for reaching 10,000 hits! I really don't deserve this!

Literal

Gratefully [even-も], 10000-hit exceeding [possessive-の] celebration illustration [object-を] received [regrettably-てしまいました]! Truly grateful [copula-です].

有難くも ('gratefully, to my humble gratitude') opens with literary humility. ~てしまいました marks the receiving as an unexpected, overwhelming event. かたじけない is an archaic/literary word for deep gratitude — much more dramatic than ありがたい, evoking samurai-era speech. The sentence is about early-2000s web culture where hit counters were milestones. The emotional excess is characteristic of Japanese internet thank-you posts.