So, you’ve found a oneshot, and you would really like the author to continue it. Do not be like purple. Purple is inconsiderate, only asking for an update. Maybe purple thinks they’re complimenting the author by asking for more, but it doesn’t come across that way. If anything, it comes across as entitled.
Be like cyan, commenting on what you like about the fic before you ask if the author will ever be interested in continuing the fic. No matter if the author is interested in updating or not, they will appreciate you far more if you compliment the fic instead of just demanding, and may even be more swayed into updating their oneshot by your kind words.
[Image description: a screenshot of two comments from two separate people on the same fic on AO3. The names of the commenters have been censored for privacy. The first commenter’s name is censored in purple, and they say, “Continue pleaseeeeeeeeee”
The second commenter’s name is censored in cyan, and they say, “Hey this Is a pretty good story I've been searching for ages a Isoldelives!au, I wish I could see what happens next, will you continue this masterpiece? (Sorry for the bad English, I'm not American)”]