When referring to a character's biography, the past tense is used. Even present-tense is discouraged at the top with "is", considering that, due to the elongation of the series timeline, some of the "alive" characters may have passed on. The present tense is used when referring to anything outside of the storyline that is not subject to temporal-effects.
That's more or less what I did, but it was reverted. Look at Claire's biography as it is now (again): "Annette GAVE Claire the instructions for creating the G-virus antidote. Claire CONTACTS Leon to take Sherry to an escape train. [...] However, she WAS thwarted once again by Birkin." The tenses constantly switch, and there are also some other unpleasent wordings like: "Claire arrived to Raccoon City in search of her brother, but found something much worse." (As if Chris was a bad thing himself, but what Claire found in Raccoon City was even worse.) When I see something like this, I usually click the Edit button and try to make the text more comfortable to read, but in this case it got reverted without a comment.
As for Ada, that's okay, I forgot that it was already mentioned above. However, I still find it impolite to just revert edits without even mentioning what was wrong. You can't learn from your mistakes like that.
I agree; when it deserves a proper response, I take the time to write a summary; this us usually in my second-revert, however. The reason why the tense is all over the place is that an editor wanted to change a particular sentence or section, and modified it to his/her own preference.
By the way, thank you for dividing my rather confusing "novel" about the RE3 Live Selections into chapters. I still need to get used to the editing tools here, so I can do that myself next time. ~ Froufrou