In the "Style/Tone" portion of the What makes a good answer? FAQ, Lauren Ipsum rightly indicates that advice about excluding autobiographical content from an answer needs to be discussed to establish a community consensus.
The following was the initial (now deleted) advice:
Avoid unhelpful autobiographical content
[Needs work. Correctness/applicability of this explanation is uncertain.]
Just as inclusion of statements such as "I am just a noob" are discouraged for questions, answers should avoid including.
Rather than stating "I am not a lawyer", a statement like "this reference seems to indicate" (or even an unspecific "from what I have heard"?) may be preferred.
When autobiographical information is helpful in evaluating the reliability of part of the answer, it should be located with the part of the answer relying on your expertise or experience.
In at least some cases, such inclusions seem to be fluff, adding no additional helpful information. (Fluff is not particularly evil but works against conciseness.)
Such can also be an indication of excessive weasel wording. Unlike Wikipedia, some weasel wording can be appropriate for a Stack Exchange answer; it can be better to provide an uncertain answer--with an indication of that uncertainty--than no answer at all. However, some people may need encouragement to avoid excessive self-deprecation (overuse of "I think", "seems", [nested] parenthetical comments, "perhaps", "maybe", etc.).
Autobiographical material which establishes a degree of expertise or experience when presenting anecdotal evidence (e.g., "In ten years as copy editor at [reputable, large publisher], I have only twice encountered that issue.") seems helpful and appropriate.
If this is reinstated (ideally with better explanation) as a guideline, it is probably important that its guideline nature is clearly stated and emphasized. A good explanation would clearly state the rationale and help those producing answers judge when autobiographical material is fluff or excessive weasel wording and when it is helpful information.