I copied the following from https://ehwiki.org/wiki/low_lolicon. From what I can gather the point is some people have no tolerance for certain tags and others are ok with a little. To satify the second group they created low versions of some tags.
Tag Type: Low Presence / Visual
Description: Indicates that the instance of lolicon does NOT pass the presence rule.
Notes: Requires the lolicon tag.
Power Requirement: 15
Slave Tags: Female
Example: The following presence examples always qualifies a normal presence tag:
25% of any sized gallery.
10 or more sequential images in an 80 or less pages gallery.
20 or more sequential images on any sized gallery.
Notes: The no. of minimal required images does not always scale up/down with the gallery size 1:1. Although a 10 sequential in 80 pages gallery is acceptable, 5 in 40 is not.
I think this is a well worded definition.
I think there is even more confusion with the use of this tag, and any "low" tag, on this site is because nhentai hasn't established any rules/guidelines in regards to "presence". It is a fundamental issue that nhentai should address because for most tags passing a presence threshold (ex. # of panels/pages or % of gallery) is an important factor when determining if a tag should be included or not. On other sites that have established presence thresholds there are certain tags like "lolicon" where instead of the usual threshold only 1-image is considered enough of a presence—"low" tags acknowledge the difference.
I hope nhentai can provide some added guidance on what presence means for this site.
An example would be if a work is 30 pages and loli appears in 3 to 5 of them. There's objectively loli present, but it's not a "loli work."
This is the definition of the tag used on E-Hentai, which is where nHentai imports from.
I haven't made any extensive "research" here on the site, but to me it seems like the tag is used in two different ways? The first is that it actually in an objective way contains lolicon, but it's not any focus on it. The second is that if it's unclear if it's actually lolicon. It might be drawn in a cartoonish way that makes it hard to get a clear opinion if the perosn is of legal age. Personally I think "lolicon" always should be used even if it doesn't have a significant presence. For sure if it's explicit. Lolicon is lolicon. But "low lolicon" is perfectly good as a modifier, when "[lolicon] does not have a significant presence in the work.". So - what I get out of this - there really needs to be a tag for young girls that possibly are of legal age but maybe not. I guess "low lolicon" fills that purpose for many? Or have I misunderstood something?
Yes that is in fact the one true meaning. This has nothing to do with agreement, anyone who disagrees is simply objectively wrong. This is what "low" means at the source where nhentai gets its doujins and tags from.