filters that start with || and end with |

[IsraeliUser]

uBO ignores the || at the beginning or the | at the end.
For example: let's say you want to block the English Wikipedia logo.
https://en.wikipedia.org/static/images/project-logos/enwiki.png

Use the filter: ||en.wikipedia.org/static/images/project-logos/enwiki.png|
uBO ignores the || at the beginning.

Use the filter:||en.wikipedia.org/static/images/*/enwiki.png|
uBO ignores the | at the end.

Use the filter: ||en.wikipedia.org/static/images/*/enwiki.pn| (without the g at the end)
uBO blocks the logo, although it should not.

uBlock Origin v1.7.0, Firefox 46.0.1 64 bit,

[lewisje]

It turns out that this creative interpretation of ABP syntax also leads these two filters from the EasyList Adware Filters supplementary list to be considered invalid:

||*-a.akamaihd.net/a24/gsd.html?$third-party
||*-a.akamaihd.net/a24/scripts/gsd.js?$third-party

It ignores both the initial || and the * after that, even though this should mean "any subdomain of akamaihd.net that ends with -a, and any subdomain of that".

[gorhill]

this creative interpretation of ABP syntax also leads these two filters [...]

It was not an interpretation issue, it was an implementation one. uBO can already deal with these filters, it's just that the wrong code path was taken for that specific case. I missed the issue re. ||*-a.akamaihd.net/... because it's a different issue that the one reported by OP.