alt Hacker NewsIANAL, so take this with a grain of salt, but:
As with all things, who are you going to get in trouble with? And what's so magical about legal practice as opposed to, say, giving shitty medical advice or telling someone how to build porch? Asking genuinely. No one falls all over themselves to say "I am not a doctor, but...", even though their next words could kill someone. The implication is that they don't have formal training but they saw something on Facebook that you should try. What happens next is on you, not on them.
> No on falls all over themselves to say “I am not a doctor, but”
This is precisely why I’m pointing this out: IANAL is a very curious case of people self-labeling their statements as “not trustworthy for the topic”. I can think of perhaps no other cases where it is so popular to claim to not be a professional in the relevant field, which suggests that IANAL is a ‘badge of honor’ rather than a proper legal disclaimer. Certainly few (if any) claim IANAD before writing about their experiences with medical issues, body things, or nutritional supplements here, even though those topics are (as you correctly indicate) potentially lethal.
Thus, IANYL: if your goal is to ensure that the recipient of your advice / opinion / whatever does not have grounds to claim that you provided legal advice, and therefore are their lawyer, then you can either do so weakly with TINLA (“this is not legal advice”), which still leaves the door open for awkward claims by some desperate grifter-rando to reach a bench, or you can do so strongly with IANYL (“I am not your lawyer”), which closes that vulnerability in full.
Not once in years of using IANYL have I seen anyone else properly protect themselves from this vulnerability; meanwhile, “IANAL but” remains in use as a badge of honor. So, yeah, I don’t think anyone considers the particular avenue of vulnerability a serious threat, and yeah, the general context of IANAL here is prideful rather than protective. But after twenty years of dealing with a stalker who was adept at internet and tried to fuck with my job at one point, I do now tend to value closing off legal vulnerabilities with certainty, and as a bonus it doesn’t imply insult to the professions of law.
IANYL, YMMV :)