Is this sentence grammatically correct, and is 'your ensuring' here an example of the subjunctive?
"We appreciate your ensuring all workstations are switched off before leaving the office locked at night."
It seems to me that "We appreciate your ensuring" could be swapped out with "We would appreciate it if you ensured", which suggests to me that 'your ensuring' is in the subjunctive mood (given that the subordinate clause of a conditional takes the subjunctive mood).
I'm curious about this because the sentence looks and feels fine to me, but I've never seen an explanation of the subjunctive which included it's appearance in this form (possessive pronoun + gerund).
Best Answer
The sentence is grammatically correct. "your ensuring..." is simply a very long gerund phrase, and can act as the complement to "We appreciate" in the normal manner.
However, as you say, the sentence could also be written "We would appreciate it if you ensured..." while remaining correct. (Note that the meaning would change slightly, as the altered sentence implies that the ensuring has not yet happened, while the original implies that it is over and done with.)
The altered sentence would simply be a conditional statement reversed from its usual order. Normally one would cast it as a conditional the following way:
"If you ensured..., we would appreciate it."
However, reversing the order of the clauses changes neither the meaning nor the correctness of the formation. Note that, as you suggested, "ensured" is in the subjunctive mood here. However, "your ensuring" not in any way subjunctive. Subjunctives are formed by using the past tense of the verb in question. "Your ensuring..." is a gerund, formed by using the present participle.