In Habitica, the plural of "To Do" is "To Do's" - with an apostrophe even though apostrophes are generally not used for plurals. This is a relatively recent change; before mid-June 2020, the official spelling was "To-Do" and "To-Dos".
The change to "To Do's" was to improve accessibility for visually impaired people. Screen reader software does not correctly pronounce "To Dos" or "To-Dos", making it sound more like "to does" or "to-DOS" with a short "o" (as in "MS-DOS"). This caused confusion for people using screen readers. Changing the plural to "To Do's" caused screen readers to pronounce it correctly.
Technically, from a grammatical perspective, using an apostrophe for a plural isn't "correct" but there is some variation to that rule for cases in which plurals are unrecognizable without an apostrophe. Examples of this can be found in internet resources such as Unusual plurals. Regardless of any potential grammatical arguments against this practice, accessibility is important and using "To Do's" makes Habitica more pleasant for people who use screen readers.
