I've had a lot of trouble figuring out how to properly search in the forum, leading to often missing that a topic has been mentioned before:

Underscores seem to get converted to spaces when searching, making it often very difficult to find mentions of a tag.
Some searches just seem to behave very oddly. For instance, searching for "searching" seems to come up with completely random posts, none of which mention anything to do with it.
Endings like "ing" seem to be simply dropped? I tried "eating", and posts come up that only have "eat".
I can't find a way to search for a phrase. At least, quotation marks seem to do absolutely nothing.

scth said:
Some searches just seem to behave very oddly. For instance, searching for "searching" seems to come up with completely random posts, none of which mention anything to do with it.

Have you got any examples of this? I clicked quite a few results and all of them had the word search somewhere in the body.

scth said:
Endings like "ing" seem to be simply dropped? I tried "eating", and posts come up that only have "eat".

This is intentional, it's called stemming. It reduces words to their stem, so the database doesn't have to index such a large dictionary, resulting in more efficient searches. Searching for eat, eaten, eating, etc. will all provide the same results because it's stripped down to the base word eat.

faucet said:
Have you got any examples of this? I clicked quite a few results and all of them had the word search somewhere in the body.

For one, topic #39232, which does come up with https://e621.net/forum_posts?search%5Bbody_matches%5D=searching. That may just be an anomaly though, since other results do seem to have at least some form of "search".

This all still sometimes makes it difficult to find topics mentioning a specific tag, though. BURs and the rest are searchable independently, but tag discussion without those can be hard to find.

scth said:
For one, topic #39232, which does come up with https://e621.net/forum_posts?search%5Bbody_matches%5D=searching. That may just be an anomaly though, since other results do seem to have at least some form of "search".

This reveals another "interesting" quirk of the forum search: it includes hyperlink targets. The guilty string can be found within Watsit's reply at the end of the thread, but only if you quote it to see the source text:

watsit said:
"created the NotPCD tag themselves":/artist_versions?search[artist_id]=58003.

I've complained about the underscores being ignored thing before, but far worse IMO is the fact that the BUR search, where the only possible results are tag names, also does this. This still hasn't been fixed.