summer newbie; summer noob
Derogatory internet slang for a young, inexperienced user who joins an online community during summer break, often seen as disruptive. The English gloss 'summerfag' is a direct but highly offensive translation; the Japanese term is also derogatory but less taboo.
When summer newbies increase, the quality of the forum goes down.
That post is totally from a summer noob.
Compound of 夏 (summer) and 厨, an abbreviation of 厨房 (kitchen), which is itself internet slang for a childish or immature user. The exact derivation of 厨房 as slang is uncertain, but it is widely used in online communities.