Dummy Subject "It" in Technical Writing

Dummy subject (extraposition) is correct. In sentences like "It is worth noting that…", "it" is a grammatical placeholder — it has no real-world referent. The real subject is the entire clause "that the default timeout is set to 30 seconds," which has been moved to the end of the sentence (extraposed). Without extraposition, the sentence would read: "That the default timeout is set to 30 seconds is worth noting" — grammatically correct but awkward and uncommon. The dummy "it" allows complex subjects to appear after the verb, making technical sentences easier to process. This is one of the most frequent constructions in formal technical and scientific English.

"It is the database that it causes the bottleneck" is incorrect. It confuses a cleft sentence with a dummy-it construction. The correct cleft sentence is: "It is the database that causes the bottleneck" — "it" here is the dummy subject of a cleft, and "that" introduces the identifying clause. Adding a second "it" before "causes" creates an error: the subject of "causes" is already "that" (referring to the database), so "it" is redundant and ungrammatical. Options A, B, and C are all correct dummy-it impersonal constructions using passive reporting verbs — these are standard in technical documentation and scientific writing.

It is the correct dummy subject here. The pattern is: It + is + adjective + to-infinitive. "It is advisable to restart the service" is a standard formal recommendation structure in runbooks and operational guides. "This" would be a demonstrative pronoun referring to something previously mentioned — it would make the sentence mean "this thing is advisable", which requires a clear antecedent. "That" is a demonstrative or relative pronoun — not used as a dummy subject. "There" is used for existential constructions: "There is a configuration error" — it introduces entities, not advisability judgements. Only "it" can serve as an impersonal dummy subject with adjectival predicates.

"It appears that the load balancer misrouted 12% of requests during the incident window" is the most appropriate. It uses the formal impersonal construction It appears that + precise clause and includes a specific, quantified finding. In post-mortems, impersonal constructions with precise data are preferred because they: (1) sound objective (no personal agent); (2) hedge appropriately (appears = not yet 100% confirmed); (3) are specific. Option A: "seems like" is informal; "had a bug" is vague. Option C: "looks as if" is informal; "was the problem" is imprecise. Option D: "feels like" is subjective and inappropriate in a technical report; ending with "it" creates an unclear pronoun reference.

"is required" is correct. In a dummy-it extraposition with a passive reporting verb (It has been established that…), the embedded clause follows normal indicative tense rules. The sentence is stating a fact: "Git LFS is required for large repositories" — this is a present passive statement of fact. "Requires" would be correct if Git LFS were the active agent: "Git LFS requires…" — but the sentence implies repositories require LFS, not that LFS requires something. "Requiring" is a participle, not a finite verb — cannot be the main verb of a that-clause. "Be required" would be correct in a subjunctive/recommendation context: "It is recommended that Git LFS be used" — but after "has been established", indicative is needed.